Biomedical subjects

K D Elgert

Publications and source records attributed to K D Elgert.

At least 19 recordsLinked to original sources

PubMed1992

Macrophages stimulated by receptor-ligand interactions exhibit differences in cell-cycle kinetics during tumor growth: stimulation at Mac-1 and Mac-3 receptors alters DNA synthesis.

Phenotypic and functional changes associated with tumor-bearing host (TBH) macrophages (M phi) are partly responsible for immunosuppression during tumor growth. Flow cytofluorometric analyses revealed differences in cell-cycle kinetics between normal host (NH) and TBH M phi that were stimulated at specific receptors. Receptor-ligand interactions were induced by antibodies against Mac-1, -2, -3, and Ia receptors and changes in DNA synthesis were measured over a 12-h time course by incorporation of propidium iodide. TBH M phi showed higher DNA synthesis than NH M phi over this time course irrespective of the receptor induced. NH M phi stimulated at the Mac-1 receptor demonstrated higher DNA synthesis than control NH M phi although TBH M phi stimulated at this receptor and control TBH M phi failed to show any differences. Both NH and TBH M phi exhibited small, short-term decreases in DNA synthesis when stimulated at the Mac-2 receptor. TBH M phi that were stimulated at the Mac-3 receptor demonstrated higher DNA synthesis than their control counterparts while NH M phi stimulated at this receptor and control NH M phi showed identical levels of DNA synthesis. No differences in DNA synthesis were found among normal or TBH M phi that were stimulated through Ia. Differences in DNA synthesis did not appear to be attributable to differences in receptor expression. Further analysis of Mac-1 and Mac-3 stimulated cells revealed that DNA synthesis in NH M phi stimulated at the Mac-1 receptor returned to control levels at 48 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Cytokines and suppressor macrophages cause tumor-bearing host CD8+ T cells to suppress recognition of allogeneic and syngeneic MHC class II molecules.

Quantitative and qualitative tumor-associated changes in T cell phenotype and function were identified in CD8+ T cells. Tumor growth changed splenic CD4+/CD8+ T cell ratios and induced the appearance of more cells with the CD8+ phenotype. In comparison to equal concentrations of normal host (NH) counterparts, tumor-bearing host (TBH) CD8+ T cells were highly suppressive to allorecognition and autorecognition. Suppression was not due to quantitative reductions in CD4+ T cells, although minor qualitative differences were observed. Suppression appeared to be mediated partly by prostaglandin E2 (PGE2). Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) contributed to TBH CD8+ T cell-mediated suppression. Blocking studies using monoclonal antibodies (mAb) in conjunction with indomethacin suggested that cytokine networks involving IFN-gamma, IL-4, and PGE2 were disrupted during tumor growth and promoted TBH CD8+ T cell suppression. Alloresponses and autoresponses were significantly suppressed when TBH CD8+ T cells mediated these reactions simultaneously with TBH Ia- macrophages. Inhibition of PGE2 production was unable to reverse the additive suppression caused by these two cell types. These results collectively suggest that tumor-induced changes in CD8+ T cells lead to suppressed allo-recognition and autorecognition through both soluble mediator molecules and cellular interactions.

Animals↗

PubMed1992

Tumor growth changes the contribution of granulocyte-macrophage colony-stimulating factor during macrophage-mediated suppression of allorecognition.

Tumor-bearing host (TBH) macrophages (M phi) suppress T cell alloresponses, and this study suggests granulocyte-macrophage colony-stimulating factor (GM-CSF), a molecule associated with suppressive M phi activity during tumor growth, signals more immunosuppression. In the absence of M phi, GM-CSF increased T cell proliferation in response to alloantigen. However, TBH M phi-mediated suppression of allorecogntion was further induced by GM-CSF. Allogeneic mixed lymphocyte reaction (MLR) cultures, containing normal host (NH) M phi, were either unaffected or enhanced. Prostaglandin E2 (PGE2), a highly suppressive monokine that decreases alloreactivity, did not seem to be involved in the suppression caused by the TBH M phi/GM-CSF interaction. M phi-CSF (M-CSF) addition to cultures did not reverse the suppression caused by TBH M phi and GM-CSF, and inhibition of PGE2 synthesis did not change the response to M-CSF. TBH Ia- M phi, a suppressor population that predominates among splenic M phi during tumor growth, demonstrated significantly lower reactivity in the presence of GM-CSF. In contrast, alloresponses suppressed by NH Ia- M phi demonstrated higher reactivity in the presence of GM-CSF. The data collectively suggest that TBH M phi respond differently to GM-CSF, and that tumor-induced changes in GM-CSF responsiveness affect M phi accessory ability.

Animals↗

PubMed1992

Tumor growth changes responsiveness to and production of granulocyte-macrophage colony-stimulating factor during recognition of self MHC class II molecules.

Tumor growth decreases T-cell recognition of self major histocompatibility complex (MHC) class II molecules by inducing changes in splenic macrophage (M phi) phenotype and function. The current investigation shows tumor-induced alterations in autorecognition also are associated with changes in responsiveness to and production of granulocyte-M phi colony-stimulating factor (GM-CSF). In contrast to normal host (NH) M phi, tumor-bearing host (TBH) M phi failed to express higher MHC class II molecule density after exposure to GM-CSF. Autoreactive T cells stimulated by either NH or TBH M phi were suppressed by GM-CSF. Inhibition of prostaglandin E2 (PGE2) synthesis reversed M-CSF-induced suppression of autoreactivity to NH M phi and, to a lesser extent, to TBH M phi. When TBH autoreactive T cells were stimulated by TBH M phi, autoreactivity increased when GM-CSF was added and PGE2 synthesis was inhibited. Although GM-CSF can contribute to tumor-induced suppression, it did not affect the contribution of GM-CSF during autorecognition. Increased GM-CSF production was responsible, at least in part, for the TBH M phi-mediated suppression. Low concentrations of GM-CSF were produced endogenously by tumor isolates, and GM-CSF production was significantly increased when isolates were stimulated with lipopolysaccharide. Autoreactive T cells stimulated solely by TBH M phi produced more GM-CSF than autoreactive T cells stimulated by NH M phi. Cultures supplemented with several concentrations of NH or TBH M phi produced similar amounts of GM-CSF in a dose-dependent manner. Inhibition of PGE2 synthesis by NH and TBH M phi reduced GM-CSF production equally. Collectively, these results suggest that during tumor growth, responsiveness to and production of GM-CSF alters recognition of self MHC class II molecules.

Animals↗

PubMed1990

Tumor modulation of autoreactivity: decreased macrophage and autoreactive T cell interactions.

The autologous mixed lymphocyte reaction (AMLR) is an in vitro measure of autoreactivity, a key mechanism in immune homeostasis. In this system, macrophages (M phi) act as accessory cells to autoreactive L3T4+ T cells by presenting self-Ia and releasing soluble modulators. During tumor growth, changes occur in M phi and T cells. Tumor-bearing host (TBH) M phi have a reduced ability to act as accessory cells. In fact, TBH M phi suppressed autoreactivity by 60-70%. The decrease in TBH M phi or T-cell abilities was not due to differences in cell numbers or incubation time. Because tumor growth causes increased prostaglandin E2 (PGE2) production by M phi, indomethacin was used to assess the contribution of prostaglandins. Normal and TBH T-cell reactivity increased nearly 50% when stimulated by normal host M phi, while normal and TBH T-cell reactivity increased nearly 100% when stimulated by TBH M phi. Thus increased prostaglandin production is partly responsible for the increased TBH suppressor M phi activity and in the normal host, suppressor M phi may be responsible for maintaining immune regulation. To assess the direct role of prostaglandins in T-cell hyporesponsiveness, PGE2 was titrated into the cultures. PGE2 suppressed normal and TBH T-cell responsiveness in a dose-dependent manner. Normal host T cells were suppressed to a greater extent than TBH T cells by PGE2 (66% versus 42% suppression, respectively). Reduced Ia expression and active suppressor mechanisms are not the only mechanisms mediating hypoautoreactivity during tumor growth. TBH autoreactive L3T4+ T cells were less responsive to self-Ia; they were only 60-80% as reactive as their normal counterparts. To address whether the helper T (TH)-cell defect involved cytokines, T cells were treated with interleukin (IL)-1, IL-2, and IL-4. In all cases, the TBH T-cell response to the factors was decreased (only 60-75% as reactive as normal T cells). Because TBH M phi-mediated suppression can override the addition of IL-1, IL-2, and IL-4, indomethacin was also added with the exogenous interleukins. This coaddition significantly enhanced normal host autoreactivity above control levels while TBH autoreactivity (the combination of TBH T cells and TBH M phi) only returned to normal host unstimulated levels. Tumor growth modulates the immune response at least by (i) decreasing the accessory cell abilities of TBH M phi through decreased Ia expression and increased production of suppressive molecules such as prostaglandins; and (ii) decreasing the responsiveness to immune enhancing factors by TH cells.

Animals↗

PubMed1990

Two-color flow cytometric analysis of the expression of MAC and MHC class II antigens on macrophages during tumor growth.

Tumor-bearing host (TBH) macrophages (M phi) exhibit immune dysfunction that is concomitant with phenotypic changes. We examined M phi subpopulations by changes in the expression of surface antigens Mac-1, -2, -3, and Ia on normal and TBH peritoneal and splenic M phi. M phi were double-labeled and analyzed by flow cytometry to observe multiple expression of surface antigens. Tumor growth alters the multiple expression of these M phi markers. Peritoneal and splenic M phi had different Mac+ and Mac+Ia+ population percentages. In TBH, peritoneal M phi had decreased percentages of Mac-1+2+, Mac-1+3+, Mac-2+3+, and Mac+Ia+ M phi. This decrease correlated with functional changes in TBH M phi. In contrast, there was an increase in Mac-2-Ia- TBH peritoneal M phi. Previously undiscovered Mac-1+2-3- and Mac-1-2-3+ populations were found. In contrast to peritoneal M phi, there was an increase in the percentage of Mac-1+2+, Mac-1+3+, and Mac-2+3+ splenic TBH M phi but, like peritoneal M phi, there was a decrease in the percentage of Mac+Ia+ M phi. Also, TBH splenic M phi showed a smaller but more uniform antigen density than normal host splenic M phi. Tumor growth modulated phenotypic alterations in peritoneal and splenic M phi subpopulations. Combined with earlier functional studies of M phi subpopulations, these data suggested a relationship between changes in M phi phenotype and tumor-induced dysfunction of M phi-modulated immune activity.

Animals↗

PubMed1990

Modulation of alloreactivity by Mac-1+, -2+, and -3+ macrophages from normal and tumor-bearing hosts: flow cytofluorometrically separated macrophages.

Macrophages (M phi) are multifunctional cells that regulate humoral and cellular immune responses. Our studies of tumor-induced M phi-mediated dysfunction used M phi subsets which were defined by their Mac-1, Mac-2, and Mac-3 surface markers. To measure the accessory activity of M phi for T cell alloreactivity, thioglycollate-elicited peritoneal M phi from normal and tumor-bearing hosts (TBH) were labeled with anti-Mac-1, -2, or -3 antibodies and separated by flow cytofluorometry. The separated Mac-1+, -2+, and -3+ M phi were called sorted M phi, while unseparated M phi were designated unsorted M phi. Both M phi types were added to mixed lymphocyte reaction (MLR) cultures at concentrations ranging from a low of 2% M phi to a high of 20% M phi. The low concentration of unsorted normal host M phi caused a 31% suppression of alloreactivity. Suppression reached 68% when high concentrations of unsorted normal host M phi were added to the MLR cultures. Unsorted TBH M phi reduced alloreactivity by 64% and 86% at low and high concentrations, respectively. When separated into subpopulations, normal host Mac-1+ M phi reduced alloreactivity by 48% and 81% when added at low and high concentrations, respectively. TBH Mac-1+ reduced alloreactivity by 31% and 59% at low and high concentrations, respectively. There were no differences in the suppression caused by normal or TBH Mac-2+ M phi, and by normal or TBH Mac-3+ M phi. Indomethacin treatment did not effect the suppression caused by Mac-1+ M phi, suggesting that proataglandin E2 was not involved. Indomethacin treatment did reduce suppression mediated by Mac-2+, -3+, and unsorted M phi. Mac-2+ M phi dramatically enhanced alloreactivity at low concentrations with normal host Mac-2+ M phi providing greater enhancement of alloreactivity than TBH Mac-2+ M phi. The division of M phi into subpopulations on the basis of Mac antigens suggested that Mac-1+ and -3+ M phi played a major role in immunosuppression in the normal host, while Mac-3+ M phi were more active in TBH immunosuppression. Because no one population of sorted TBH M phi was more suppressive than sorted normal host M phi, we suggest that tumor-induced immunosuppression may involve a network of suppressor M phi.

Animals↗

PubMed1990

Normal and tumor-bearing host splenic macrophage responses to lipopolysaccharide.

Lipopolysaccharide (LPS) was used to assess the responses of normal and tumor-bearing host (TBH) macrophages (M phi) to activation signals. M phi were incubated with LPS for either 3 hr or 24 hr and then assayed for phenotypic, functional, or cell-cycle changes. A 3-hr LPS treatment had no significant effect on M phi phenotype. In contrast, the 24-hr LPS treatment caused a significant decrease in the percentage of normal host Mac+ and Ia+ M phi. In the TBH, a 24-hr LPS treatment caused an increase in the percentage of Mac-1+ and -2+ M phi and a decrease in the percentage of Mac-3+ and Ia+ M phi. When normal host M phi were plated for 24 hr (control), there was an increase in Mac-1+ and -2+ M phi and a decrease in Ia+ M phi. The 24-hr TBH control showed a decrease in Mac-1+ and Ia+ M phi. To assess functional changes, LPS-treated normal and TBH M phi were added to the allogeneic mixed lymphocyte reaction (MLR) or the autologous MLR (AMLR). There were no significant differences in M phi accessory activity after a 3-hr LPS treatment. A 24-hr LPS treatment of normal host M phi also had no effect. A 24-hr LPS treatment of TBH M phi led to a significant decrease in allogeneic T-cell reactivity, and even the 24-hr TBH control showed significant suppression of T-cell responsiveness. In the AMLR, a measure of autoreactive T-cell responsiveness, a 3-hr LPS treatment had no affect on normal host M phi but led to increased accessory ability in TBH M phi. TBH M phi, however, were still less than 50% as responsive as normal host M phi even after LPS treatment. The 24-hr LPS treatment caused a significant decrease in normal or TBH M phi accessory activity. A 24-hr plating of normal host M phi decreased their accessory ability. In addition to the phenotypic and functional changes after LPS treatment, M phi cell-cycle kinetics were also investigated. The percentages of normal host M phi in G0/G1 were not changed significantly after a 3-hr LPS treatment. In contrast, M phi plated for 24 hr with or without LPS had a decreased percentage of cells in G0/G1. Normal host M phi showed little change in total RNA levels after a 3-hr treatment but had increased RNA levels after a 24-hr treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Tumor-induced alteration in macrophage accessory cell activity on autoreactive T cells.

Using a tumor-model system, differences in the accessory cell capabilities on autoreactive T cells of splenic macrophages from normal and tumor-bearing hosts (TBH) were assessed in the syngeneic mixed lymphocyte reaction. Tumor development caused a drop in autoreactivity. At 0 and 7 days of tumor growth, no drop in reactivity occurred when TBH macrophages were used as accessory cells and L3T4+ autoreactive T cells from normal mice were used as responder cells. However, by day 14, there was a 32% drop in reactivity, and by day 21 only 22% of the T cell reactivity remained when TBH macrophages were used as accessory cells. Alterations in macrophage Ia antigen during tumor growth were first investigated as the potential cause of reduced autoreactivity. Before tumor growth (day 0) 59% of the splenic macrophages were found to be Ia+. Day-7 TBH macrophages showed no difference in Ia antigen expression when compared to day 0 macrophages. However, by day 14, TBH macrophages showed a 9% decrease, and by day 21 they showed a 36% decrease in the number which were Ia+. Concomitant with the decrease in the number of Ia+ cells was a decrease in the density of Ia antigen expression on day-14 and -21 TBH macrophages. In day-14 and -21 TBH macrophages, two populations were seen that were Ia+. The first had a 10%-20% decrease in Ia antigen expression per cell while the second population had a greater than 50% drop in Ia antigen expression per cell. By titrating and mixing TBH macrophages with normal host macrophages, we assessed whether they could actively mediate suppression of autoreactive T cells. A titratable suppressive phenomenon was demonstrated using day-21 TBH macrophages. In contrast, day-7 and -14 TBH macrophages titrated with normal host macrophages had no effect on the syngeneic mixed lymphocyte reactivity. Lastly, we investigated whether the macrophage-mediated suppression was caused by increased prostaglandin secretion. Addition of indomethacin to cultures increased autoreactive T cell reactivity stimulated by normal or TBH macrophages (59% and 99% increase, respectively). Although indomethacin reduced suppression mediated by TBH macrophages, autoreactivity did not return to levels induced by untreated or indomethacin-treated cells from a normal host. Taken together, the data suggested that tumor growth modulates the function of macrophage accessory cells with autoreactive T cells in at least two ways: by decreasing Ia antigen expression and by increasing suppressor activity.

Animals↗

PubMed1989

Tumor-induced variations in a high molecular weight inhibitory monokine.

A soluble inhibitor of T cell proliferation was demonstrated in splenic and peritoneal macrophage (M phi) culture supernatants and was variably glycosylated during tumor development. This factor(s) inhibited mixed lymphocyte reaction- (MLR) and concanavalin A-induced T cell proliferation and was not prostaglandin E2 (PGE2), as demonstrated by size (nondialyzable, found in a 30 kilodalton [kd] ultrafiltration retentate and in fractions corresponding to greater than 67 kd on S-200 Sephacryl chromatography) and time course of activity in the MLR. Concentrated supernatants were PGE2-free and yet inhibited proliferation in the MLR. Isoelectric focusing (IEF) revealed normal and tumor-bearing host (TBH) concentrated M phi supernatants' major peaks of inhibitory activity differed in charge, with a pI of 6.5-7.6 for normal hosts and 4.0-6.0 for TBH. Activity in TBH M phi supernatants was found primarily in fractions eluting from hydroxylapatite at 0.3 M sodium phosphate buffer, pH 7.3, was resistant to proteolytic enzymes, but was sensitive to neuraminidase. In contrast, inhibitory activity in normal host M phi supernatants eluted from hydroxylapatite at 0.6 M sodium phosphate buffer and was not sensitive to neuraminidase. Thus, variable glycosylation (presence and absence of sialic residues) could account for the charge difference seen in IEF and may have a bearing on tumor-induced hyporesponsiveness. Kinetic addition of supernatants to the MLR revealed PGE2 may be required for inhibitory activity to be manifested early (0 and 24 h) but not if the high molecular weight (mw) inhibitor was added late (48 and 72 h post initiation). Both normal and TBH M phi supernatants suppressed the generation of interleukin 2 (IL 2) with a dose- and time-dependent difference. Cell-cycle analysis of mitogen-stimulated cells treated with normal and TBH M phi supernatants revealed that TBH M phi supernatants enhanced cell-cycle progression when measured early, but that both normal and TBH M phi supernatants suppressed the number of cells in S phase when measured late in the assay. The production of a high mw inhibitor by both normal and TBH M phi could suggest a homeostatic mechanism, which was upset by increased PGE2 production and production of an inhibitor containing sialic acid, tipping the balance in favor of immunosuppression.

Animals↗

PubMed1989

Changes in macrophage populations: phenotypic differences between normal and tumor-bearing host macrophages.

As a tumor grows, changes occur in the function of macrophages (M phi). This is concomitant with changes in their phenotype. Flow cytometric analysis of monoclonal antibody (mAb)-labeled thioglycollate-elicited peritoneal, and resident splenic, M phi showed a tumor-induced shift of Mac-1, -2, -3, and Ia antigen expression. During tumor growth, the percentage of peritoneal Mac-2+, -3+, and Ia+ M phi decreased significantly (22%, 14%, and 58%, respectively), while Mac-1+ M phi remained unchanged. By analyzing the data on two-dimensional histograms and comparing the sizes of M phi to cell-surface antigen expression, we identified distinct subpopulations of peritoneal M phi. Three distinct size versus antigen expression M phi subpopulations were detected by flow cytometry and consisted of 10-16, 17-22, and 23-27 microns for the small-, medium-, and large-sized populations, respectively. Large-sized Mac-1+ and -2+ M phi decreased (37% and 38%), while large-sized Mac-3+ M phi did not decrease during tumor growth. Medium-sized Mac-3+ M phi decreased 33% during tumor growth, while no differences could be seen in medium-sized Mac-1+ or -2+ M phi. Concomitant with the decrease in large-sized Mac-1+ M phi was an increase in small-sized Mac-1+ M phi. Peritoneal Ia+ M phi were mostly small-sized (4-7-fold increase over the medium-sized and none in the large-sized population). M phi Ia antigen expression was nearly absent in the 21-day tumor-bearing host, with less than 4% of the cells labeling positive (a 73% drop from normal host M phi). In splenic M phi, the percentage of Mac-1+ M phi significantly increased (90%) during tumor growth, while Mac-2+ and -3+ M phi showed a smaller, but still significant, increase (48% and 40%, respectively). Additionally, splenic Ia+ M phi significantly decreased (29%) during tumor growth. More important than the decreased cell numbers was the significant decrease in Ia antigen expression per cell. Unlike the peritoneal M phi, the splenic M phi did not show distinct size versus antigen expression subpopulations, although there was an overall difference in M phi size between normal and TBH. These data suggested that M phi from different anatomical sites are phenotypically different and tumor growth mediates phenotypic alterations in peritoneal and splenic M phi populations. This may be the source of tumor-induced dysfunction of M phi-mediated immune activity.

Animals↗

PubMed1987

Prostaglandin E2 production by Mac-2+ macrophages: tumor-induced population shift.

Tumor growth induced a shift in the phenotype of macrophages (M luminal diameter) responsible for factor-mediated suppression of allogeneic mixed lymphocyte reactions (MLR), and the suppression by tumor-bearing host (TBH) Mac-2+ M luminal diameter was in part due to production of prostaglandin E2 (PGE2). Thioglycollate-elicited peritoneal M luminal diameter from normal and TBH BALB/c mice were modulated with anti-Mac-1, -2, or -3 monoclonal antibodies (mAb) or depleted with mAb plus complement and cultured in the presence or absence of indomethacin. Culture supernatants derived from mAb plus complement-depleted M luminal diameter were added to the MLR at time of initiation and showed that the suppressor phenotype shifted from Mac-3+ in the normal host to Mac-2+ in the TBH. Mac-1+ M luminal diameter also appeared to be involved in suppression by normal host, but not TBH, M luminal diameter. Loss of MLR suppression (increase in MLR reactivity) correlated with an increase in protein content of the culture supernatants. In an effort to explain both this relationship and the mechanism of MLR suppression, PGE2 levels of culture supernatants were determined by radioimmunoassay. Mac-1+ M luminal diameter were involved in the regulation of PGE2 production in normal hosts, as both activation and depletion caused an increase in PGE2 production. Depletion caused a more dramatic increase in PGE2 production than did activation, suggesting that Mac-1+ M luminal diameter had a dampening effect on PGE2 production. In contrast, no Mac-1+ M luminal diameter-mediated regulatory function occurred in the TBH. Mac-3+ M luminal diameter were involved in the regulation of PGE2 production in both normal and TBH. Mac-2+ M luminal diameter were the primary producers of PGE2 in the TBH, but not in the normal host, as their depletion in the TBH caused a significant loss of PGE2 production. Thus, immunosuppression in the TBH was at least partly due to the inability of Mac-1+ and/or Mac-3+ M luminal diameter to control production of PGE2 by Mac-2+ M luminal diameter.

Animals↗

PubMed1987

Shifts in macrophage (M phi) surface phenotypes during tumor growth: association of Mac-2+ and Mac-3+ M phi with immunosuppressive activity.

Rat anti-mouse monoclonal antibodies (mAb), anti-Mac-1, -2, and -3, directed against macrophage (M phi) glycoprotein surface antigens, were used to demonstrate a tumor-induced shift in peritoneal M phi subpopulations. This study of the tumor-induced shift was approached in two steps. First, to show that separate phenotypic M phi subpopulations existed and second, to show that a shift in these populations was involved in immunosuppression of the host during tumor growth. Endogenous peroxidase activity was examined among normal and tumor-bearing host (TBH) M phi. A significant increase in the number of peroxidase-positive M phi occurred during tumor growth. Indirect immunofluorescence showed a decrease in Mac-2+ cells and an increase in Mac-3+ cells in TBH M phi populations. When the mAb, anti-Mac-1,-2, and -3 were used in the presence of complement (C), they were cytotoxic for M phi and showed differential depletion of normal and TBH M phi. Peroxidase-positive TBH M phi were susceptible to C-mediated lysis by anti-Mac-1 and -3 but not by anti-Mac-2, whereas no direct relationship was observed among normal host M phi. To demonstrate differences between normal and TBH M phi subpopulations, soluble inhibitory factors were examined from mAb plus C-modified M phi populations. Anti-Mac plus C-treated normal and TBH M phi produced supernatants with different regulatory capabilities as assessed in the mixed-lymphocyte reaction (MLR). Anti-Mac-2 plus C treatment significantly reduced the ability of TBH M phi to produce a soluble suppressor(s) but did not alter normal host M phi-derived suppressor production. In contrast, anti-Mac-1 and -3 plus C treatment of normal host M phi significantly reduced suppressor production. In the TBH, however, anti-Mac-1 plus C had no effect, while anti-Mac-3 plus C had only a limited reduction as compared to the normal host. Determination of levels of prostaglandin E2 (PGE2) in M phi supernatants showed that normal host Mac-1+ M phi were involved in down regulation of PGE2 production. This control was missing in the TBH M phi. Mac-2+ M phi were the apparent producers of PGE2 which accounts for the factor-mediated MLR suppression attributed to TBH Mac-2+ M phi. Collectively, these data suggest that tumor-induced aberrations in immunoregulation can in part be attributed to differences in anti-Mac mAb-defined M phi subpopulations.

Animals↗

PubMed1986

Variations in macrophage antigen phenotype: a correlation between Ia antigen reduction and immune dysfunction during tumor growth.

Variable Ia antigen expression by macrophages (M phi) was examined during tumor growth by measuring: Ia antigen masking and immunofluorescence by anti-Ia antibody, accessory cell function in concanavalin A (Con A) and mixed lymphocyte reaction (MLR)-induced T cell proliferation, and M phi stimulatory function in the MLR. Tumor-induced progressive loss of Ia antigen expression was shown by immunofluorescence and corroborated by anti-Ia blockade of MLR stimulatory activity of normal but not tumor-bearing hosts (TBH) splenic M phi. The TBH splenic M phi supported Con A-induced proliferation of syngeneic T cells (Ia antigen-independent) but did not support syngeneic T cell proliferation in the MLR (Ia antigen-dependent). Irrespective of tissue source, normal and TBH M phi differed in their MLR stimulatory capabilities. In general, splenic M phi preparations were better stimulators of allogeneic T cell blastogenesis in the MLR than thioglycollate-elicited peritoneal M phi. Kinetic studies with TBH M phi showed a significant progressive loss in MLR stimulatory activity, which was especially pronounced with peritoneal M phi. Expression of Ia antigens by normal but not TBH M phi were diminished by 24-h in vivo plating of the peritoneal M phi. Indomethacin treatment showed Prostaglandin E2 was not a direct in vitro factor in Ia antigen-mediated reduction of splenic M phi MLR stimulatory activity. Taken together, these data delineate a loss of M phi Ia antigen expression, resulting in a decrease in Ia antigen-mediated functional activities during tumor growth.

Animals↗

PubMed1986

Changes in splenic macrophage Mac antigen expression during tumor growth: a kinetic study of accessory cell function and antigen-defined phenotypes.

Three monoclonal antibodies, anti-Mac-1, -2, and -3, were used to modify accessory cell activity of whole spleen cell (WSC) or splenic adherent cell (SAC) preparations from normal or tumor-bearing hosts (TBH). Ligand activation by anti-Mac-1, -2 and -3 modified normal and TBH WSC lectin responses differentially; the most pronounced effect was with anti-Mac 1, which augmented normal WSC responsiveness, whereas anti-Mac-2 and -3 augmented TBH WSC mitogenesis. Ligand interaction with Mac-2 epitopes resulted in significantly suppressed normal host WSC responsiveness. With complement, anti-Mac-1 and -3 each reduced normal and TBH WSC proliferation. Reconstitution of blastogenesis was obtained by combining Mac-2-depleted with Mac-3-depleted normal host WSC or by combining Mac-1-depleted with Mac-2-depleted TBH WSC. To evaluate the role of different types of splenic adherent cells in T cell lectin responsiveness, adherent cells were collected and depleted by antibody plus complement treatment and added back to normal T cells. Removal of TBH SAC indicated the number of Mac-1+ SAC susceptible to lysis increased during tumor growth, whereas those susceptible to anti-Mac-2 and -3 treatment decreased. Removal of Mac-1+ normal host SAC stimulated the supportive accessory function of the remaining SAC. Enhancing accessory cell function diminished after removal of Mac-2+ or Mac-1+ normal and TBH SAC, respectively. T cell responsiveness was increased by adding back combinations of normal host SAC, Mac-1-depleted with Mac-3-depleted SAC or Mac-1-depleted with Mac-2-depleted SAC but not by Mac-2-depleted with Mac-3-depleted SAC. In contrast, none of the TBH SAC combinations were completely restored in accessory activity. In summary, SAC from normal host demonstrated an accessory cell function corresponding to a Mac-1- phenotype, which was either replaced or obscured by the predominance of a Mac-1+ phenotype in TBH.

Animals↗

PubMed1986

Splenocytes from tumor-bearing Corynebacterium parvum treated mice maintain interleukin-2 and -3 activity.

Systemic and local administration of the bacterium Corynebacterium parvum (more accurately known as Propionibacterium acnes) is reported to exert antitumor action via activated macrophages or short-lived cytotoxic T lymphocytes (CTL), respectively. This study examined the effect of C. parvum treatment on resulting in vitro interleukin levels, which are components in the sequence of events leading to the development of effective CTL. C. parvum administration prevented palpable fibrosarcoma development. This was concomitant with restoration and maintenance of normal interleukin-2 (IL-2) and interleukin-3 (IL-3) levels and prevention of suppressor cell development in mice injected with both tumor cells and vaccine. Our finding of C. parvum-induced maintenance of IL-2 and IL-3 levels and apparent lack of suppressor cell formation lends support to the idea of local C. parvum antitumor action possibly being mediated by CTL arising via the interleukin cascade.

Animals↗

PubMed1986

An improved data analysis method for interleukin 2 microassay.

Development of the interleukin 2(IL 2) microassay, coupled with the use of highly purified or recombinant factors has allowed a detailed examination of the mechanism of action of this important biological response modifier. However, probit analysis of the microassay data does not allow inherent error of the system to be approximated nor can units of activity be assessed for significance. A computer program was developed to analyze the validity of each regression line and to generate 95% confidence intervals around each line. This program employs analysis of variance, linear regression analysis and the parallel line assay to fix confidence intervals for each IL 2 unit value. The use of recombinant IL 2 as an immunomodulator in clinical settings warrants a more precise statistical method to evaluate normal fluctuations of this factor than currently in use. The development of such a method is presented here.

Biological Assay↗

PubMed1984

Interleukin 2 (IL-2) activity during tumor growth: IL-2 production kinetics, absorption of and responses to exogenous IL-2.

A temporal study assessed the relationship between fibrosarcoma growth and immunologic encumbrance due to the inability of BALB/c mouse splenocytes to elaborate the lymphokine Interleukin 2 (IL-2). Nylon-wool fractionation and antiserum treatments suggested the existence of a mildly nylon-wool-adherent, anti-Lyt 2-sensitive tumor-induced suppressor T (Ts) cell which significantly decreased IL-2 activity. Absorption investigations indicated that ligand-activated tumor-bearing host (TBH) spleen cells were less receptive to IL-2 than their normal counterparts. When splenocytes were antiserum treated before absorption, removal of Lyt 2+ (suppressor T) cells resulted in greater IL-2 absorption by the remaining cells. Purified IL-2 only partially restored suppressed TBH spleen cell mitogen- or alloantigen-induced blastogenesis; whereas, normal host reactivity was significantly augmented. The collective data suggest that TBH spleen cells were capable of producing IL-2 and of responding to the IL-2 amplification signal when tumor-induced Ts cells were depleted.

Absorption↗