Biomedical subjects

S H Golub

Publications and source records attributed to S H Golub.

At least 19 recordsLinked to original sources

PubMed1995

Granulocyte-macrophage colony-stimulating factor and interleukin-4 differentially regulate the human tumor necrosis factor-alpha promoter region.

Regulation of TNF-alpha promoter activity by IL-2, IFN-gamma, GM-CSF, and IL-4 was examined in the U937 macrophage cell line and the MLA 144 T cell line. Using a transient transfection system, the full-length TNF-alpha promoter was examined for response to these cytokine signals. Only GM-CSF was able to consistently induce a twofold activation of the TNF-alpha promoter in the U937 cell line. GM-CSF activation of the promoter region was further analyzed using a series of 5' truncations and site mutations of the AP-1, AP-2, and CRE sites of the promoter. The GM-CSF activation mapped to the region contained within the 95 base pairs upstream from the transcription start site (TSS) with the AP-2 site as a putative cis-acting sequence. IL-4 profoundly inhibited both basal and phorbol ester-induced TNF-alpha promoter activity as well as protein production. Promoter inhibition by IL-4 required the 95-bp basal promoter sequence.

Animals↗

PubMed1994

Interleukin-7 selectively enhances natural kill cytotoxicity mediated by the CD56bright natural killer subpopulation.

Both the CD56bright and CD56dim NK cell subpopulation mediate non-major histocompatibility complex-restricted cytolysis of NK-sensitive tumor cell lines, and IL-2-dependent augmentation of cytolysis and proliferation of CD56bright and CD56dim NK cells was recently reported. We investigated the effects of IL-7 and IL-6 on the killing mediated by these cells to determine whether other cytokines besides IL-2 regulate their activity. IL-7 increased the cytotoxicity in only the CD56bright NK cell population. The effect of IL-7 varied from donor to donor but was comparable to that of IL-2. Furthermore, IL-7 was found to induce lymphokine-activated killer (LAK) cell generation primarily in the CD56bright cells. CD56bright NK cells also proliferated in response to IL-7, but only weakly in comparison with IL-2. In contrast to the results with CD56bright NK cells, IL-7 had little effect on the CD56dim subset. However, IL-2 enhanced NK cytotoxicity, induced LAK activity, and caused proliferation of these cells. An anti-IL-2 antibody did not inhibit the IL-7-induced increase in CD56bright cytotoxicity, suggesting that IL-7 acted independently of IL-2. However, the IL-7 effect on CD56bright NK cell cytotoxicity was partially inhibited by anti-CD2, anti-CD11a, and anti-CD18 antibodies and almost completely abrogated by a combination of anti-CD2 and anti-CD11a. These data suggest that cell adhesion molecules (CAM) play a role in the regulation of IL-7-induced CD56bright NK cell cytolysis. In contrast to IL-7-mediated effects, IL-6 alone had no effect on CD56+ NK cell cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, CD↗

PubMed1993

IL-4 inhibits IL-2 induction of LAK cytotoxicity in lymphocytes from a variety of lymphoid tissues.

The purpose of this study was to determine the influence of recombinant human interleukin-4 (IL-4) on the regulation of lymphokine-activated killer (LAK) and mixed lymphocyte culture cytotoxic activity. Lymphocytes from several lymphoid tissues were studied including human peripheral blood leukocytes (PBL), spleen cells, thymocytes, and thoracic duct lymphocytes. Cells were cultured with IL-4 in the presence or absence of recombinant human interleukin-2 (IL-2) in 4-day cultures. LAK and natural killer (NK) activities were measured in a standard chromium release cytotoxicity assay against LAK-sensitive, NK-resistant M14 melanoma targets and NK-sensitive K562 erythroleukemic cells. IL-4 alone does not increase NK or LAK activity under the conditions studied. However, IL-4 does inhibit the induction of cytotoxic activity by IL-2. IL-4 inhibits IL-2-induced thymidine incorporation in 3-day PBL cultures, suggesting that the inhibition of cytotoxicity is not a dilution effect due to the proliferation of noncytotoxic cell populations. IL-4 also inhibits the development of LAK and NK-like activities generated in mixed lymphocyte culture (MLC) while augmenting MLC-generated allospecific cytotoxic T lymphocyte activity. Thus, IL-4 appears to inhibit the induction of nonspecific cytotoxic effectors while augmenting the generation of MHC-specific responses. This confirms an important regulatory function for this lymphokine in the generation of cytotoxic effectors.

Cell Division↗

PubMed1993

Interleukin-6 is a mediator of TNF-alpha regulation of LAK cell function.

TNF-alpha at 50-100 U/ml synergizes with IL-2 in enhancing LAK activity and IL-6 production in low-dose IL-2 (1-10 U/ml) culture of human PBL. High-dose TNF-alpha (> or = 200 U/ml) has less effect and even sometimes resulted in lowering of both LAK activity and IL-6 production below control levels. TNF-alpha-mediated regulation of low-dose IL-2 activation occurs even at late stages (effector phase) of LAK development. IL-6, as previously reported, acts at late stages of low-dose IL-2 culture to enhance LAK, but does not stimulate TNF-alpha production. The combined addition of TNF-alpha and IL-6 to late stages of IL-2 culture does not produce any additive or synergistic effect on LAK. We tested for the relative roles of TNF-alpha and IL-6 in late stage regulation of LAK development with antibodies (Abs) to these cytokines. Anti-IL-6 Ab abrogates late phase LAK enhancement by TNF-alpha, while anti-TNF-alpha Ab has no effect on IL-6 augmentation of LAK cytotoxicity. IL-2 added to PBL culture at doses greater than 10 U/ml induces production of both TNF-alpha and IL-6. Addition of anti-TNF-alpha Ab at late stages of high-dose IL-2 (> or = 20 U/ml) culture decreases both LAK cytotoxicity and IL-6 production, and the inhibition of LAK is reversed by the addition of IL-6. By contrast, anti-IL-6 Ab decreases LAK cytotoxicity, but does not alter TNF-alpha production, and the inhibition of LAK is not reversed by addition of TNF-alpha. These data indicate that TNF-alpha is important for both LAK development and IL-6 secretion in PBL, and that IL-6 is the proximate mediator in TNF-alpha regulation of these cytotoxic cell functions.

Cells, Cultured↗

PubMed1993

Pulmonary surfactant inhibits interleukin-2-induced proliferation and the generation of lymphokine-activated killer cells.

The generation of lymphokine-activated killer (LAK) cell activity and the proliferative response to human recombinant interleukin-2 (IL-2) were significantly reduced when either human peripheral blood lymphocytes (PBL) or purified CD56+/CD3- lymphocytes were cultured in the presence of pulmonary surfactant. Surfactant concentrations ranging between 30 and 500 micrograms/ml produced increasing levels of inhibition ranging from 20 to 95%. For any given concentration of surfactant, increasing the IL-2 concentration produced increasing levels of LAK activity but never overcame the suppressive effects of the surfactant. Time course studies demonstrated that surfactant is inhibitory only if added to PBL during the first 2 days of IL-2 culture, suggesting a preferential action during the induction phase of LAK activity. Pretreatment of PBL with surfactant for as little as 2 to 4 h inhibited their subsequent response to IL-2 culture, suggesting that inhibition is rapid, persistent, and directly due to alterations in PBL responsiveness. To determine if surfactant alters cell membrane function, we measured the effects of surfactant exposure on LAK:tumor binding. Binding of LAK cells to both K562 and M14 tumor targets was inhibited in a concentration-dependent manner. Concurrently, we observed a reduced expression of IL-2 alpha-chain receptors on surfactant-treated CD56+/CD3- cells and a dramatic reduction in the expression of adhesion molecules including CD2, LFA-1, LFA-3, and ICAM-1. We conclude that pulmonary surfactant has the potential to suppress cytotoxic and proliferative responses to IL-2, alters cell-to-cell interactions, and reduces the expression of activation and adhesion molecules on LAK cells.

Adult↗

PubMed1992

The regulation of the human tumor necrosis factor alpha promoter region in macrophage, T cell, and B cell lines.

The 1311-base pair human tumor necrosis factor (TNF) alpha promoter region was fused to the luciferase (Luc) reporter gene and studied in a transient transfection system in three TNF producing cell lines, the U937 macrophage cell line, the MLA 144 T cell line, and the 729-6 B cell line. This full length promoter construct can be induced by phorbol 13-myristate acetate (PMA) in each of these cell types. Analysis of a series of 5'-truncations showed several peaks of basal and PMA induced activity suggesting the presence of several positive and negative regulatory elements. A PMA responsive element was localized to a region between -95 and -36 bp relative to the transcription start site. Within this region, single AP-2- and AP-1-like consensus sequences were noted. These AP-2 and AP-1 sites were each modified with a double point mutation. A modest (20-50%) reduction in TNF promoter activity was observed with the AP-2 site mutation. However, mutation of the AP-1 site markedly diminished both the basal and PMA-activated promoter activity. Also co-transfections of the wild-type promoter construct with an AP-1/c-jun expression vector resulted in augmented basal and PMA-induced promoter activity.

B-Lymphocytes↗

PubMed1992

IL-6 enhances the cytotoxic activity of thymocyte-derived CD56+ cells.

Thymocyte-derived lymphokine-activated killer (LAK) cells were used as a model for the study of the cytokine driven development of cytotoxicity. These cells are devoid of initial cytotoxic activity but upon culture in IL-2 they develop into cytotoxic effectors. The parameters of the response of thymocytes to IL-6 are similar to that of PBL in that IL-6, at concentrations as low as 1 mu/ml, increases cytotoxicity of thymocyte-LAK cells when generated in low doses (25-50 mu/ml) of IL-2. IL-6-enhanced thymocyte-LAK cytotoxicity is observed when tested against both NK-resistant and NK-sensitive tumor cell lines. IL-6 alone does not induce any cytotoxicity from thymocytes nor does IL-6 change the time course of thymocyte-LAK cell generation in IL-2 culture. IL-6 does not affect DNA synthesis, total cell number, proportion of CD56+ cells, or the expression of IL-2R (both P55 and P75 glycoproteins) in IL-2-cultured thymocytes. Instead, IL-6 used to treat mature thymocyte-LAK effector cells for as little as 1 hr prior to 51Cr-release assay increases LAK cytotoxicity. This enhancement is abrogated by pretreatment of effector cells with cycloheximide, suggesting that protein synthesis is required for IL-6 to enhance LAK cell activity. The precursor phenotypes of IL-6-responsive thymocyte-LAK cells are CD3-/CD5-. The effector phenotypes of IL-6-enhanced thymocyte-LAK cells are CD5-/CD56+. Thus, IL-6 depends on synthesis of rapid-turnover proteins to act on mature CD56+/CD5- LAK cells to increase their cytotoxic function.

Antigens, CD↗

PubMed1992

Modulation of natural killer and lymphokine-activated killer cell cytotoxicity by lactoferrin.

Natural killer (NK) and lymphokine-activated killer (LAK) cell cytotoxic functions can be strongly augmented by the iron-carrier protein lactoferrin (LF). LF significantly enhances NK and LAK activities when added at the beginning of NK or LAK cytotoxicity assays. LF is effective in augmenting cytotoxic activities at concentrations as low as 0.75 microgram/ml, and higher concentrations of LF induce greater augmentation of NK and LAK. Iron does not appear to be essential for LF to increase NK and LAK, as depleting iron from LF with the chelator deferoxamine does not affect the capacity of LF to increase cytotoxicity. LF is known to have RNase enzymatic activity, and LF enhancement of NK and LAK can be blocked by RNA. However, LFs from two different sources with over 100-fold difference in RNase activity are equally effective in enhancing NK and LAK. Furthermore, purified non-LF RNase does not modulate NK or LAK activity and DNA is as effective as RNA in blocking LF augmentation of NK or LAK cytotoxicity. Therefore, the RNase activity is unlikely to be responsible for LF enhancement of the cytotoxicities. Newborn infants are known to have low NK activity and NK and LAK cells have been implicated in host defense against microbial infections. Thus, maternal milk-derived LF may have a role in boosting antimicrobial immunity in the early stages of life. In adults, LF released from neutrophils may enhance NK and LAK functions in the inflammatory process induced by microbial infections.

Cells, Cultured↗

PubMed1991

Immunopathological features of human pulmonary tumors following low-dose interleukin-2.

We administered preoperative low-dose interleukin-2 (IL-2) to 10 patients undergoing thoracotomy for pulmonary tumors. The in vivo effect of IL-2 on tumor-associated lymphocyte activity was assessed in the resected specimens by immunohistochemistry and compared with observations in 45 patients who did not receive IL-2. H & E evaluation revealed an increase in intra- and peritumoral lymphocyte infiltration in the IL-2-treated patients. Immunopathological evaluation with monoclonal antibodies revealed that this lymphocyte infiltration was predominantly CD5-positive T cells. The amount of intra- and peritumoral lymphocyte activity correlated with the dose of IL-2 administered (6000-90,000 international units/kg every 8 h for 48 h. IL-2-treated patients showed increases in T-cell-associated activation markers (IL-2 alpha-receptor, transferrin receptor and HLA-DR) on peritumoral lymphocytes, but not on intratumoral lymphocytes. We previously reported that low-dose IL-2 increases the intrinsic natural killer cell cytotoxicity of intratumoral lymphocytes and suggest that this lymphocyte infiltration is further evidence that low-dose IL-2 can augment in vivo lymphocyte activity at the tumor site.

Aged↗

PubMed1991

Characteristics of interleukin-6-enhanced lymphokine-activated killer cell function.

To study the effect of IL-6 on the development of cytotoxic cells, we examined lymphokine-activated killer (LAK) activity generated from human nonadherent PBL. Addition of rIL-6 at the initiation of 5-day PBL cultures significantly increases LAK activity in the presence of low concentrations (between 5 and 25 u/ml) of rIL-2. RIL-6 alone induces no PBL LAK activity but at doses as low as 0.8 u/ml rIL-6 enhances LAK activity with optimal enhancement of LAK at 5.0 u/ml of rIL-6. This enhancement is independent of effects on cells growth as rIL-6 did not affect the cell recovery of PBL cultured in rIL-2. RIL-6-enhanced LAK is mediated by the same type of effector cells as those of LAK from rIL-2 alone with effector cells primarily generated from large granular CD3-negative E rosetting lymphocytes. RIL-6 does not change the time course of LAK development and pretreatment of PBL with rIL-6 has no effect on the PBL response to subsequent rIL-2 induction of LAK. Addition of rIL-6 to LAK cultures 2 hr before the cytotoxicity assay shows equal enhancement as addition at the initiation of the culture. However, rIL-6 requires the presence of both rIL-2 and another factor in the supernatant from LAK cultures in order to enhance LAK. Our results indicate that IL-6 can modulate LAK activity at a very late stage of LAK development, and that the enhancement by IL-6 is dependent on the presence of IL-2 and another soluble factor generated during rIL-2 culture.

Cells, Cultured↗

PubMed1990

TNF-alpha and IFN-gamma reverse IL-4 inhibition of lymphokine-activated killer cell function.

Recombinant IL-4 inhibits IL-2-induced lymphokine-activated killer (LAK) cell development of PBMC. We evaluated the effect of various cytokines in reversing IL-4-mediated LAK inhibition. PBMC were cultured in IL-2 (10-1000 u/ml) with or without IL-4 (2-100 u/ml) and tested for cytotoxicity against the NK-sensitive K562 cells and NK-resistant UCLA-SO-M14 cells. Addition of IL-4 at the beginning of culture suppresses LAK activity in a dose-dependent fashion. Addition of IFN-gamma or TNF-alpha partially reverses IL-4-mediated inhibition (30-100%) in a dose-dependent fashion. IFN-gamma and TNF-alpha must be added within the first 24 hr of initiating culture in order to reverse IL-4 inhibition. Furthermore, IFN-gamma and TNF-alpha are most effective at reversing IL-4 inhibition at low concentrations of IL-2 (less than 100 u/ml). Addition of other IL-2-induced cytokines such as GM-CSF (50 u/ml), M-CSF (250 u/ml), and IFN-alpha (10-10,000 u/ml) fails to reverse IL-4 inhibition. In addition to suppression of LAK induction, IL-4 also inhibits IL-2-induced IFN-gamma and TNF-alpha protein production in PBMC. The reversal of IL-4-mediated LAK inhibition by TNF-alpha and IFN-gamma may therefore be due to resupply of these endogenously suppressed cytokines.

Colony-Stimulating Factors↗

PubMed1990

IL-1 and IL-4 as reciprocal regulators of IL-2 induced lymphocyte cytotoxicity.

Interleukin 4 (IL-4) suppresses the interleukin 2 (IL-2) induced lymphokine-activated killer (LAK) cell development from human peripheral blood mononuclear cells (PBMC). Suppression is observed at high (1,000 U ml-1) as well as low (10 U ml-1) concentrations of IL-2. IL-4 needs to be present at the beginning of the IL-2 culture to exert the suppressive effect. IL-4 also inhibits the development of CD25 (Tac) antigen on the PBMC cultured in IL-2. Interleukin 1 (IL-1) can reverse the suppressive effect of IL-4 on LAK induction when added at the early phase of the IL-2 culture. IL-1 enhances IL-2 induced LAK development, which may partially explain the reversion of IL-4 inhibition by IL-1. IL-1 also reverses the inhibitory effect of IL-4 on the development of CD25 antigen expression, although IL-1 alone does not enhance the induction of CD25 expression in PBMC cultured by IL-2. Furthermore, IL-4 suppresses IL-2 induced IL-1 production in PBMC. Thus, suppression of CD25 may be a pathway for the suppression of LAK induction. The expression of CD56 is not directly associated with the expression of LAK activity. IL-4, IL-1 or combination of the two cytokines has no effect on IL-2 induced expression of CD56. These results indicate that IL-4 has an antagonistic effect and IL-1 has a synergistic effect on IL-2-induced LAK development.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1990

The heterogeneity of target recognition by lymphokine-activated killer precursor cells.

Lymphokine-activated killer (LAK) cells were generated from peripheral blood lymphocytes (PBL) that were depleted of mature cytotoxic natural killer (NK) cells. PBL NK activity was abolished by pretreatment of effector cells with the toxic lysosomotropic agent L-leucine methyl ester (LME) or by depletion of effector cells by K562 monolayer absorption (MA). Both treatments markedly reduced the proportion of cells expressing NK-associated markers such as CD 16 (Leu 11b, B73.1), Leu 7, and NKH-1 (Leu 19), whereas these treatments had minimal effects on cells expressing T cell markers (CD 3, CD 4, and CD 8). LME and MA also drastically decreased the proportion of K562 target-binding lymphocytes. LAK activity against NK-sensitive and NK-resistant targets can be generated from the NK cell-depleted PBL by incubation with interleukin-2. Peak LAK activity generated from MA-treated PBL was later than the peak of LAK activity generated from either untreated or LME-treated PBL. Although MA of PBL on NK-resistant S4 sarcoma targets had little effect on NK activity, LAK activity against both K562 and S4 targets was reduced. These results suggest that there are at least three LAK precursor subpopulations in PBL: mature NK cells that can bind and kill K562 targets (LME-sensitive and MA-sensitive); "pre-NK" cells that can bind but cannot kill (LME-resistant and MA-sensitive); and non-NK cells that cannot bind and cannot kill K562 targets (MA-resistant).

Antigens, CD↗

PubMed1990

Differential regulation by interleukin-4 and interferon-gamma of an autologous melanoma-specific cytotoxic T-cell clone and the tumor-infiltrating lymphocytes from which it was established.

To investigate the specificity of human tumor-infiltrating lymphocytes (TIL) against autologous tumors, TIL from five metastatic melanoma patients were expanded with rIL-2 and assessed for cytotoxicity in chromium release assays. TIL from a patient showing preferential cytotoxicity against autologous melanoma cells were further analysed. TIL were cloned by limiting dilution. Four out of 27 clones showed substantial cytotoxicity against autologous melanoma and one clone, designated as No. 8a-5 (CD3+, CD4-, CD8+, CD56-), selectively killed autologous melanoma but did not kill six different allogeneic melanoma, K562, or autologous or allogeneic Con A lymphoblast targets. Cytotoxicity of No. 8a-5 cells was inhibited by anti-HLA class I MAb (w6/32), by anti-beta 2-microglobulin MAb, and by anti-CD3 (OKT3) MAb, suggesting that the specific cytotoxicity was HLA class I-restricted and that the clone utilized the T-cell receptor complex for recognition of targets. Pretreatment with rIFN-gamma increased the sensitivity of autologous melanoma targets to lysis by No. 8a-5 cells. Exogenous rIL-4 enhanced [3H]TdR incorporation by these TIL. In contrast, rIFN-gamma reduced the sensitivity of the autologous melanoma to lysis by uncloned TIL, and rIL-4 suppressed the cytotoxicity and cell proliferation of uncloned TIL. These results indicate that both specific and non-specific cytotoxic cells can be developed from the same TIL and that these can be differentially regulated.

Antibodies, Monoclonal↗

PubMed1990

A pilot study of intralymphatic interleukin-2. I. Cytotoxic and surface marker changes of peripheral blood lymphocytes.

Patients with metastatic solid tumors were treated with six escalating doses of weekly intralymphatically injected recombinant interleukin 2 (i.l. IL-2). Nine patients completed the treatment and were evaluated for immunologic features of their peripheral blood lymphocytes (PBLs). The patients' PBL counts increased 4 days after the first i.l. IL-2 injection. The cell counts remained higher than baseline in week 6 prior to the last i.l. IL-2 injection. However, the PBL number decreased below baseline 1 day after the sixth injection, and recovered to normal levels after 3 days more. Natural killer (NK) activity showed similar changes when calculated as total activity per ml of blood. In vitro 1 h treatment of PBLs with IL-2 greatly enhanced NK cytotoxicity. The enhancement was only slight in the first week of i.l. IL-2 treatment, but was significantly greater on day 35 (7 days after dose 5) and day 39 (4 days after dose 6). In contrast, the increase was similar to the baseline on day 36, the day after the sixth injection. No lymphokine-activated killer activity was detected in the patients' PBLs with or without short-term in vitro IL-2 treatment. Besides the NK cytotoxic function, lymphoid subpopulations were evaluated numerically for total T cells (CD3/OKT3), T-cell subsets (CD4/OKT4 and CD8/OKT8), B cells (OKB7), NK cells (CD56/NKH1/Leu19, CD16/Leu11), and monocytes/NK cells (CD11b/OKM1). The activation markers (HLA-DR, CD25/Tac, and CD38/OKT10/Leu17) were also included. Intralymphatic IL-2 treatment had no effect on the PBL surface marker expression in the first week of treatment. However, by week 6, the percentages of cell populations expressing the NK-associated antigens CD56, CD16, and CD11b were significantly increased. In contrast, the percentage of CD3-positive T cells showed no change or a marginal decrease. Prior to and after i.l. IL-2 treatment, the CD56-positive cells in the PBLs were predominantly CD16 positive and CD3 negative. The i.l. IL-2 treatment did not induce PBL proliferation, or changes in the expression of CD25 (Tac), HLA-DR, CD38, CD4, CD8, CD57, or OKB7 in the patients' PBL. These results indicate that i.l. IL-2 treatment does affect the total number of PBLs, the cells expressing NK activity, and NK-associated surface markers.

Antigens, Differentiation↗

PubMed1989

Inhibition of lymphokine-activated killer cell function by human alveolar macrophages.

Tissue- and organ-specific factors may be important in the regulation of cytotoxic lymphocytes. We therefore examined the ability of human alveolar macrophages (AMs) to alter the tumoricidal function of lymphokine-activated killer cells (LAK cells). AMs, obtained by bronchoalveolar lavage from healthy volunteers, or peripheral blood monocytes were added to a standard 4-h chromium release LAK assay at varying concentrations. AMs severely inhibited the killing of both NK-sensitive (K562) and NK-resistant (M14) tumor cells [42 +/- 2.6% (SEM) inhibition of M14 killing at the 0.125:1 AM:LAK ratio and 83 +/- 2.3% inhibition at the 1:1 ratio, n = 9]. Peripheral blood monocytes, in contrast, were only one-eighth as inhibitory as AMs. A positive smoking history was associated with a 3- to 7-fold increase in the number of AMs recovered by bronchoalveolar lavage but had no effect on the inhibition produced per AM cell. The mechanism of inhibition was investigated. Formalin fixation produced an 8-fold reduction in the inhibitory capacity of AMs, suggesting the need for active metabolism or an intact cell membrane. No soluble mediator could be detected with a two-chamber Transwell system, in 24-h AM culture supernatants, or following blocking experiments with indomethacin, catalase, or superoxide dismutase. Binding studies demonstrated selective binding between LAK cells and AMs, yet AMs were not susceptible to LAK-mediated lysis under the usual assay conditions. In summary, AMs are potent inhibitors of in vitro LAK function. Inhibition requires direct cell contact and is independent of soluble reactive oxygen species, prostaglandins, or activation by tobacco smoking. Inhibition is not due to lysis of the AM as a competitive cold target. These results suggest that AMs may actively limit antitumor cytotoxic responses in the lung.

Cell Communication↗

PubMed1989

Inhibition of lymphokine-activated killer- and natural killer-mediated cytotoxicities by neutrophils.

Peripheral blood polymorphonuclear neutrophils (PMN) can significantly inhibit lymphokine-activated killer- (LAK) mediated cytotoxicity when added to a cytotoxicity assay of IL-2-activated PBL and target cells. The inhibition by resting PMN is resistant to blocking with catalase and superoxide dismutase, suggesting that reactive oxygen species are not involved. The addition of TNF greatly enhanced the PMN-mediated inhibition of LAK effector functions. This TNF-enhanced inhibition is reversed by catalase, but not by superoxide dismutase, implicating hydrogen peroxide in the augmented inhibition. Separation of PMN from effector cells and target cells totally abrogates the inhibition by both resting PMN and TNF-treated PMN. Formalin-fixed PMN, heat-treated PMN, PMN lysates, and PMN membrane all fail to mediate any inhibition of LAK. These results suggest that contact with intact viable PMN is needed for inducing LAK inhibition. However, pretreatment of LAK cells with PMN also decreases their cytotoxicity in subsequent chromium release assays. PMN can also inhibit NK cytotoxicity of fresh PBL. However, NK activity is much less sensitive to inhibition by resting PMN than is LAK. TNF also augments PMN inhibition of NK, and there is no significant difference between LAK and NK in sensitivity to the TNF-enhanced inhibition. Our results indicate that PMN can significantly influence the destruction of tumor targets by LAK and NK, and suggest that approaches to circumvent such regulation may be important in the outcome of immunotherapies with IL-2 and LAK cells.

Cell Communication↗

PubMed1989

The inhibitory effect of human interferon alpha on the generation of lymphokine-activated killer activity.

The generation of lymphokine-activated killer (LAK) activity and the proliferative response to human recombinant interleukin-2 (IL-2) were significantly reduced by the presence of human recombinant leukocyte interferon (IFN alpha) in cultures of human peripheral blood mononuclear cells (PBMC). Mature natural killer (NK) cells can be depleted from PBMC with the toxic lysosomotropic agent L-leucine methyl ester. The generation of cytotoxic cells from lymphocytes depleted in leucine methyl ester was also inhibited by indicating that the IFN-alpha effect is not limited to mature cytotoxic NK cells. Depletion of adherent cells from PBMC did not affect the suppression of LAK induction by IFN-alpha. Surface marker analyses of Tac antigen and transferrin receptor (TfR) showed that the presence of IFN alpha throughout the culture period significantly suppressed the typical increase in IL-2-induced Tac- and TfR-positive cells. In contrast, IFN alpha treatment before and after IL-2 culture enhanced LAK cytotoxic activity. Therefore, combinations of these biological response modifiers for clinical use should take into account the dual effect of IFN alpha on key features of the IL-2 response.

Humans↗