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D F Jelinek

Publications and source records attributed to D F Jelinek.

At least 55 records · Page 3Linked to original sources
PubMed1991

Delineation of the functional capacity of human neonatal lymphocytes.

Neonatal T cell-B cell collaboration was investigated utilizing a system of T cell-dependent polyclonal B cell activation and Ig secretion. In this system, T cells activated by immobilized anti-CD3 provide a potent stimulus for Ig production by adult lymphocytes. By contrast, anti-CD3 stimulation of cord blood lymphocytes generated minimal numbers of Ig-secreting cells. Ig production by neonatal lymphocytes was enhanced by the addition of Staphylococcus aureus or secreted factors from mitogen-stimulated adult T cells. Supplementation with IL-2 resulted in the production of large amounts of IgM and small amounts of IgG and IgA, with less Ig produced than by comparable cultures of adult lymphocytes. Neonatal T cells proliferated and produced IL-2 in response to immobilized anti-CD3, and supported B cell proliferation and Ig secretion by adult B cells, although not as effectively as adult T cells. Supernatants from activated neonatal T cells were markedly limited in their capacity to support Ig production by adult B cells. Neonatal B cells could be induced to differentiate in response to anti-CD3-stimulated adult T cells. However, the amounts of IgG and IgA secreted were small compared to adult levels. These studies indicate a relative, but not absolute, functional deficiency of both neonatal B and T cells.

Adult↗
PubMed1990

Structure of the rat gene encoding cholesterol 7 alpha-hydroxylase.

Cholesterol 7 alpha-hydroxylase (7 alpha-hydroxylase) is a microsomal cytochrome P-450 that catalyzes the first and rate-limiting step in bile acid biosynthesis, the major catabolic pathway in cholesterol homeostasis. The gene encoding the rat 7 alpha-hydroxylase has been isolated and characterized. Southern blotting experiments demonstrated that the gene is present in a single copy in the rat genome. DNA sequence analysis showed that the 7 alpha-hydroxylase gene is unique among the characterized cytochrome P-450s in that it contains only six exons. Nuclease S1 and primer-extension mapping experiments positioned the 5'-ends of the 7 alpha-hydroxylase mRNA approximately 20-25 nucleotides downstream of a consensus TATAAA sequence. RNA blotting experiments demonstrated the presence of multiple 7 alpha-hydroxylase mRNAs that differ in the lengths of their 3'-untranslated regions.

Amino Acid Sequence↗
PubMed1990

Cloning and regulation of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis.

The rate-limiting step in bile acid biosynthesis is catalyzed by the microsomal cytochrome P-450 cholesterol 7 alpha-hydroxylase (7 alpha-hydroxylase). The expression of this enzyme is subject to feedback regulation by sterols and is thought to be coordinately regulated with enzymes in the cholesterol supply pathways, including the low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl-coenzyme A reductase and synthase. Here we report the purification of rat 7 alpha-hydroxylase and the determination of a partial amino acid sequence. Oligonucleotides derived from peptide sequence were used to clone a full-length cDNA encoding 7 alpha-hydroxylase. DNA sequence analysis of the cDNA revealed a 7 alpha-hydroxylase protein of 503 amino acids with a predicted molecular weight of 56,890 which represents a novel family of cytochrome P-450 enzymes. Transfection of a 7 alpha-hydroxylase cDNA into simian COS cells resulted in the synthesis of a functional enzyme whose activity was stimulated in vitro by the addition of rat microsomal cytochrome P-450 reductase protein. RNA blot hybridization experiments indicated that the mRNA for 7 alpha-hydroxylase is found only in the liver. The levels of this mRNA increased when bile acids were depleted by dietary cholestyramine and decreased when bile acids were consumed. Dietary cholesterol led to an increase in 7 alpha-hydroxylase mRNA levels. The enzymatic activity of 7 alpha-hydroxylase paralleled the observed changes in mRNA levels. These results suggest that bile acids and sterols are able to alter the transcription of the 7 alpha-hydroxylase gene and that this control explains the previously observed feedback regulation of bile acid synthesis.

Amino Acid Sequence↗
PubMed1990

In vitro autoantibody production by normal adult and cord blood B cells.

To investigate the repertoire of autoantibodies in humans, anti-DNA and rheumatoid factor (RF) production in vitro was assessed in cultures of adult peripheral blood B cells and neonatal umbilical venous blood B cells. B cells were stimulated under various culture conditions, using an immobilized monoclonal anti-CD3 antibody and adult T cells or Staphylococcus aureus (SA) in the presence or absence of adult T cells or factors derived from mitogen-stimulated adult T cells as polyclonal B cell activators. Total IgM, as well as IgM anti-DNA and RF, were assessed by ELISA. Total IgM production was induced from adult and neonatal B cells with SA plus T cell factors, as well as anti-CD3-stimulated T cells. RF was induced from adult and cord blood B cells by either mode of stimulation, whereas significant anti-DNA production was observed only when B cells were stimulated with anti-CD3-activated T cells. These results confirm the presence of B cell precursors for autoantibodies in the preimmune as well as normal adult repertoire, and indicate that the production of anti-DNA and RF appears to be regulated independently.

Adult↗
PubMed1989

Immunomodulatory role of IL-4 on the secretion of Ig by human B cells.

The effect of IL-4 on the production of Ig by human B cells was examined. Highly purified B cells were stimulated with Staphylococcus aureus (SA) and IL-4 alone or in combination with various other cytokines and the supernatants assayed for Ig by isotype-specific ELISA. IL-4 (10 to 100 U/ml) did not support Ig secretion by SA-stimulated blood, spleen, or lymph node B cells, whereas IL-2 supported the production of all isotypes including IgE. Moreover, IL-4 suppressed the production of all isotypes of Ig by B cells stimulated with SA and IL-2 including IgG1, IgG2, and IgE. IL-4-mediated suppression was partially reversed by IFN-gamma or -alpha and low m.w. B cell growth factor. TNF-alpha and IL-6 did not reverse the IL-4-induced suppression of Ig production. The inhibitory action of IL-4 on Ig production appeared to depend on the polyclonal activator used to stimulate the B cells. Thus, Ig secretion by B cells activated by LPS and supported by IL-2 was not inhibited by IL-4. Whereas IL-4 alone supported minimal Ig production by LPS-activated B cells, it augmented production of all Ig isotypes in cultures stimulated with LPS and supported by IL-2. IFN-gamma further enhanced production of Ig in these cultures. When the effect of IL-4 on the responsiveness of B cells preactivated with SA and IL-2 was examined, it was found not to inhibit but rather to promote Ig production modestly. A direct effect of IL-4 on the terminal differentiation of B cells was demonstrated using B lymphoblastoid cell lines. IL-4 was able to enhance the Ig secreted by an IgA-secreting hybridoma, 219 and by SKW6-CL-4, an IL-6-responsive IgM-secreting EBV transformed B cell line. These results indicate that IL-4 exerts a number of immunoregulatory actions on human B cell differentiation. It interferes with the activation of B cells by SA and IL-2, but promotes the differentiation of preactivated B cells, B cell lines, and B cells activated by LPS without apparent isotype specificity.

Adjuvants, Immunologic↗
PubMed1988

Inhibitory influence of IL-4 on human B cell responsiveness.

The role of IL-4 in human B cell activation, proliferation, and differentiation was examined. rIL-2, but not rIL-4, was able to promote maximum proliferation and generation of Ig-secreting cells in cultures of highly purified B cells stimulated with Cowan I Staphylococcus aureus (SA). Addition of rIL-4 to rIL-2-supported cultures of SA-stimulated peripheral blood, spleen, or lymph node B cells dramatically suppressed both proliferation and differentiation. Results from experiments in which rIL-4 was added to culture at progressively later times indicated a requirement for rIL-4 to be present during the first 2 days of a 5-day incubation to cause inhibition of responsiveness. When a two-stage culture system was utilized, rIL-4 was found to support proliferation or differentiation of B cells initially activated with SA for 2 days only minimally. However, rIL-4 did not inhibit responses of SA preactivated B cells supported by IL-2. The presence of rIL-4 during the initial 48-h activation of B cells with SA and rIL-2 resulted in a profound inhibition of the ability of the activated B cells to respond subsequently to rIL-2 or lymphokine-rich T cell supernatants. A similar 48-h incubation with rIL-4 alone without SA had no effect on subsequent B cell responsiveness. The presence of rIFN-gamma during B cell activation decreased the inhibitory effect of IL-4. Other cytokines including IFN-alpha, IL-1, and commercially available low m.w. B cell growth factor also diminished the inhibitory effect of IL-4. These results indicate that IL-4 inhibits the capacity of human B cells to be activated maximally by SA and rIL-2 and therefore suggest a new immunomodulatory role for this cytokine.

Antigens, Surface↗
PubMed1988

T cell-dependent activation of B cell proliferation and differentiation by immobilized monoclonal antibodies to CD3.

The capacity of mAb directed at the CD3 molecular complex (64.1) to induce T cell-dependent B cell proliferation and differentiation was examined. Coculture of B cells with mitomycin C-treated T4 cells (T4 mito) stimulated by immobilized 64.1 resulted in marked B cell proliferation and Ig-secreting cells (ISC) generation in the absence of any additional stimulation. The magnitude of the B cell responses induced by immobilized 64.1-stimulated T4 mito was far greater than that induced by other stimuli, such as Staphylococcus aureus plus factors produced by mitogen-activated T cells, PWM, or soluble 64.1. The induction of maximal B cell responsiveness required direct contact between activated T cells and responding B cells. Of note, immobilized 64.1 also induced B cell proliferation and ISC generation in the presence of mitomycin C-treated T8 cells. By contrast, immobilized 64.1 stimulated T4 or T8 cells that had not been treated with mitomycin C induced very modest ISC generation and suppressed B cell responses supported by T4 mito even in the presence of exogenous IL-2 or factors produced by mitogen-activated T cells. The interactions between T and B cells in these cultures not only induced B cell responses, but also enhanced the production of IL-2 by activated T cells. Increased IL-2 production was facilitated when culture conditions afforded the opportunity for contact between B cells and activated T cells. These results indicate that the establishment of interactions between B cells and anti-CD3-stimulated T4 or T8 cells provides all of the signals necessary for proliferation and differentiation of B cells without other stimuli and also augments the production of lymphokines by the activated T cells. The data emphasize the role of Ag-nonspecific interactions between B cells and T cells in promoting polyclonal responses of both cell types.

Adult↗
PubMed1988

Regulation of human B lymphocyte responsiveness.

Regulation of human B cell responses is a complex process involving the activities of a variety of cells and cytokines. There are important differences between the regulation of human and murine B lymphocytes, especially with regard to the action of IL2 and IL4. In man, IL2 appears to play a central role in regulating B cell activation, proliferation and differentiation, whereas IL4 plays a regulatory role by inhibiting initial B cell activation. Above and beyond providing regulatory cytokines, activated human T cells can also directly stimulate B cell differentiation by a process that requires cellular contact. A better understanding of the nature of signal transduction during interactions between B cells and activated T cells and provided by the various cytokines should provide additional insight into the regulation of B cell function in man.

Antibody Formation↗
PubMed1987

Enhancement of human B cell proliferation and differentiation by tumor necrosis factor-alpha and interleukin 1.

The role of tumor necrosis factor-alpha (TNF-alpha) in human B cell responses was examined and compared with that of interleukin (IL) 1 by assessing the ability of each cytokine to support proliferation and differentiation. Recombinant TNF-alpha (rTNF-alpha) and recombinant IL-1 (rIL-1) each enhanced the generation of immunoglobulin-secreting cells (ISC) in cultures of pokeweed mitogen-stimulated B cells incubated with T cells. To examine the direct effect of rTNF-alpha and rIL-1 on the responding B cell, highly purified peripheral blood B cells were stimulated with Cowan I Staphylococcus aureus (SA). In the absence of T cell factors, proliferation was minimal and there was no generation of ISC. Recombinant IL-2 (rIL-2) supported both responses. Although rTNF-alpha alone did not support SA-stimulated generation of ISC, it did increase SA-stimulated B cell DNA synthesis by two- to eightfold. In addition, rTNF-alpha augmented B cell proliferation in rIL-2 supported SA-stimulated cultures. Moreover, rTNF-alpha enhanced the generation of ISC stimulated by rIL-2 alone or rIL-2 and SA. rIL-1 also augmented DNA synthesis and generation of ISC by B cells stimulated with SA and rIL-2. However, rTNF-alpha enhanced proliferation and ISC generation in SA + rIL-2-stimulated cultures even when they were supplemented with saturating concentrations of rIL-1. Utilizing a two-stage culture system, it was found that the major effect of rTNF-alpha was to enhance responsiveness of SA-activated B cells to rIL-2, whereas it exerted only a minimal effect during initial stimulation. These results indicate that TNF-alpha as well as IL-1 augment B cell responsiveness. Moreover, the ability of rTNF-alpha to enhance B cell responsiveness was not an indirect effect resulting from the induction of Il-1 production by contaminating monocytes, but rather resulted from the delivery of a signal by rTNF-alpha directly to the responding B cell that promoted both proliferation and differentiation after initial activation. The data therefore indicate that human B cell responsiveness can be independently regulated by the action of two separate monocyte-derived cytokines.

B-Lymphocytes↗
PubMed1987

Comparative activation requirements of human peripheral blood, spleen, and lymph node B cells.

Human peripheral blood, spleen, and lymph node B cells were stimulated with Cowan I Staphylococcus aureus (SA) or F(ab')2 fragments of anti-mu antibody (anti-mu) and various lymphokines and were analyzed for proliferation and generation of Ig-secreting cells (ISC). SA alone but not anti-mu stimulated minimal proliferation of each population. Recombinant IL 2 (r-IL 2) effectively promoted proliferation of SA-stimulated blood and spleen B cells, but supported less vigorous responses of lymph node B cells. By contrast, r-IL 2 enhanced DNA synthesis of all anti-mu-stimulated B cells early in culture, but did not promote sustained proliferation of anti-mu-stimulated lymph node B cells and only promoted ongoing DNA synthesis of some anti-mu-activated blood (eight out of 17) and spleen (five out of 14) B cell preparations. Recombinant interferon-gamma (r-IFN-gamma) and a commercial preparation of B cell growth factor (BCGF) also augmented DNA synthesis of all three B cell populations stimulated with SA or anti-mu early in culture, but neither alone was able to sustain maximal proliferation. Markedly enhanced sustained proliferation of all three anti-mu- and SA-stimulated B cell populations was noted when cultures were supported by the combination of r-IL 2 and BCGF, or to a lesser extent by r-IL 2 and r-IFN-gamma. The generation of ISC from SA-stimulated blood or spleen but not lymph node B cells was effectively supported by r-IL 2 alone. Differentiation of lymph node B cells required the combination of r-IL 2 and BCGF. These studies emphasize the importance of both the activation stimulus and the origin of the B cells in determining the lymphokine requirements of human B cell responsiveness.

B-Lymphocytes↗
PubMed1987

Development of a cell with dendritic morphology from a precursor of B lymphocyte lineage.

Cells developing dendritic morphology were detected in cultures of highly purified human B cells incubated with 4 beta-phorbol 12-myristate 13-acetate (PMA). After 72 hr of culture, 2 to 7% of the cells had assumed a dendritic shape provided that contact with a plastic or glass surface also occurred. Dendritic cells developed in cultures of B cells prepared by positively selecting cells that stained with the B cell-specific monoclonal antibody B1 with the fluorescence-activated cell sorter. By contrast, dendritic cells could not be detected in cultures of cells obtained from patients with Bruton's type agammaglobulinemia that lacked B cells. Cells with dendritic morphology were nonspecific esterase negative and not phagocytic. They expressed HLA-DR, DQ, and DP antigens, receptors for interleukin 2 and transferrin, and were stained by B1 and 60.3, an antibody that identifies the beta-chain common to lymphocyte function associated antigen-1, complement receptor 3, and the p150,95 antigen, but not by monoclonal antibodies to monocytes, complement receptors 2 or 3, NK cells, T cells, or Langerhans' cells. Formation of dendritic cells was inhibited by microtubule poisons (vinblastine, colchicine), a microfilament inhibitor (cytochalasin B), and the 60.3 monoclonal antibody, but not by inhibition of DNA synthesis. These data indicate that a subset of B cells is capable of assuming dendritic morphology after stimulation with phorbol esters and attachment to a surface. These dendritic cells exhibit characteristics that are quite similar to the interdigitating cells found in T cell-dependent areas of lymph nodes.

Antibodies, Monoclonal↗
PubMed1987

Inhibition of human B cell responsiveness by prostaglandin E2.

The capacity of prostaglandin E2 (PCE2) to modulate human peripheral blood B cell proliferation and the generation of immunoglobulin-secreting cells (ISC) stimulated by Cowan 1 strain Staphylococcus aureus and mitogen-stimulated T cell supernatant was examined. PGE2 significantly inhibited both responses, whereas PGF2 alpha had no inhibitory effect. Responses of highly purified B cells obtained from spleen, lymph node, and tonsil were also inhibited. In addition PGE2 suppressed B cell responses supported by recombinant interleukin 2 rather than T cell supernatant. PGE2-mediated inhibition was mimicked by forskolin, a direct activator of adenylate cyclase. Kinetic studies indicated that PGE2 inhibited B cell responses by a progressively greater increment as cultures were prolonged. Evaluation by flow cytometry after staining with acridine orange or mithramycin indicated that PGE2 had no effect on initial B cell entry into the G1 phase of the cell cycle, passage through G1, and entry into S, G2, and M. Rather, PGE2 inhibited responses of postdivisional daughter cells. PGE2 inhibited responses in cultures stimulated by the calcium ionophore ionomycin and T cell supernatant but had minimal effects in cultures stimulated by the combination of ionomycin and phorbol myristate acetate. Moreover, phorbol myristate acetate reversed PGE2-mediated inhibition of proliferation stimulated by S. aureus or S. aureus + T cell supernatant. These results indicate that PGE2 suppresses the continued growth and differentiation of human B cells, although it has no effect on initial B cell activation and suggest that PGE2 may play a role in regulating human B cell responses in vivo.

B-Lymphocytes↗
PubMed1986

The roles of interleukin 2 and interferon-gamma in human B cell activation, growth and differentiation.

The roles of interleukin 2 (IL 2) and interferon-gamma (IFN-gamma) in human peripheral blood B cell activation, growth and differentiation were examined. Highly purified B cells stimulated with Cowan I Staphylococcus aureus (SA) proliferated minimally and generated no immunoglobulin-secreting cells (ISC) without the addition of T cell supernatants (T sup) produced by mitogen-activated T cells. Recombinant IL 2 (rIL 2) alone was able to promote maximum proliferation and generation of ISC in cultures of highly purified SA-stimulated B cells when present from the initiation of the incubation. IFN-gamma, by contrast, could not support either response alone. When a two-step culture system was employed to determine the effect(s) of T cell influences during both initial activation and in propagating the response following activation, it was found that B cells activated by SA alone subsequently responded maximally to T sup but only minimally to IL 2 and not at all to IFN-gamma. However, the presence of T sup, rIL 2, or rIFN-gamma during initial activation with SA was found to facilitate greatly the subsequent capacity of the activated B cells to proliferate and differentiate in response to either T sup or IL 2. These data suggest two distinct pathways of human B cell responsiveness. Activities in T sup other than IL 2 or IFN-gamma can support the growth and differentiation of B cells initially activated with SA alone, whereas rIL 2 is capable of promoting these responses maximally only when B cells have been initially activated by SA in the presence of T cell lymphokines, such as IL 2 or IFN-gamma. The results emphasize the role of specific T cell factors in determining the outcome of humoral immune responses.

B-Lymphocytes↗
PubMed1986

Human peripheral blood B lymphocyte subpopulations: functional and phenotypic analysis of surface IgD positive and negative subsets.

Highly purified human peripheral blood B cells stimulated with Cowan I Staphylococcus aureus (SA) and mitogen-activated T cell supernatants (T supt) generated large numbers of immunoglobulin (Ig)-secreting cells (ISC), whereas fewer ISC developed in cultures containing T supt in the absence of SA. To determine whether surface Ig isotype expression defined responsive B cell subsets, IgD+ and IgD- B cells were prepared with the fluorescence-activated cell sorter. Whereas both the IgD+ and IgD- B cells responded to SA + T supt, only the IgD- subset generated substantial numbers of ISC in response to T supt alone. Analysis of secreted Ig revealed that IgG and IgA were the predominant isotypes secreted by IgD- B cells in response to T supt or SA + T supt. By contrast, the IgD+ cells secreted predominantly IgM in response to SA + T supt but not to T supt alone. When responsiveness to pokeweed mitogen (PWM) was examined in the presence of supplemental T cells, the IgD- subset was found to be greatly enriched for responsive cells, and again, IgG and IgA were the predominant isotypes secreted, although these cells were also capable of secreting some IgM. The magnitude of the response induced by PWM from IgD- B cells was usually greater than that induced by SA + T supt. Although IgD+ B cells responded poorly to PWM, the differentiation of a small number of IgM-secreting cells was routinely stimulated by this polyclonal activator in the presence of T cells. The magnitude of the PWM response by IgD+ B cells was always greatly diminished compared with that stimulated by SA + T supt. Cell cycle analysis after acridine orange staining, cell volume measurement, and staining for expression of activation antigens (transferrin receptor and 4F2) indicated that the IgD- B cells were largely resting, but did contain a population of activated cells. Removal of activated 4F2+ cells from the IgD- subset diminished but did not abolish their capacity to generate ISC in response to SA + T supt or PWM in the presence of T cells. These results suggest that the IgD- population contains both an activated 4F2+ and a resting 4F2- subset. The data emphasize that multiple subpopulations of peripheral blood B cells contain precursors of ISC. Moreover, the responsiveness of the subsets to various stimuli and the Ig isotype subsequently secreted appear to be intrinsic features of each subset.

Adult↗
PubMed1985

Regulation of human B cell activation by prostaglandin E2. Suppression of the generation of immunoglobulin-secreting cells.

The role of prostaglandin E2 (PGE2) in the generation of immunoglobulin-secreting cells (ISC) from human peripheral blood B cells was examined. Initial studies demonstrated that monocyte (M phi)-mediated suppression of the generation of ISC in Staphylococcus aureus (SA)-stimulated cultures was mitigated by indomethacin, and thus suggested that the cyclooxygenase pathway products of arachidonic acid played a role in the regulation of B cell activation. The possibility that PGE2, one of the major products of this pathway generated by M phi-affected human B cell responses, was therefore investigated. PGE2 was found to cause concentration-dependent inhibition of the generation of ISC in pokeweed mitogen- or SA-stimulated B cell cultures supported by T cells. Studies were therefore carried out to determine whether PGE2 inhibited the production of necessary T cell factors or directly altered B cell responsiveness. Initially, the effect of PGE2 on the capacity of mitogen-stimulated cells to secrete a factor that supported the differentiation of B cells into ISC was investigated. Excessive numbers of M phi or PGE2 inhibited the production of B cell differentiation factor from mitogen-stimulated T cells. The effect of PGE2 on the capacity of B cells to differentiate into ISC was more complex. PGE2 inhibited the generation of ISC when B cells were stimulated with SA and B cell differentiation factor-containing T cell supernatants. PGE2-mediated inhibition of ISC generation was observed even when addition of PGE2 was delayed until after ISC first were detected in culture. By contrast, PGE2 caused only minimal inhibition of the generation of ISC cultures stimulated by T cell supernatants alone or protein A-free SA and T cell supernatants. These results suggested that SA-responsive B cells were particularly sensitive to inhibition by PGE2. Additional experiments supported the conclusion that B cell sensitivity to inhibition by PGE2 is augmented by the immunoglobulin cross-linking effects of protein A-containing SA. Overall, the results support the conclusion that PGE2 at physiologically relevant concentrations can influence human antibody responses by means of a direct inhibitory action on the responding B cell or an indirect one on the production of necessary T cell factors.

B-Lymphocytes↗
PubMed1985

The roles of T cell factors in activation, cell cycle progression, and differentiation of human B cells.

The relationship of the T cell influences involved in human B cell activation and differentiation into immunoglobulin-secreting cells (ISC) was investigated. T cell supernatants (T supt) generated by stimulating T cells with phytohemagglutinin and phorbol myristate acetate contained activities capable of augmenting DNA synthesis and the growth of mitogen-stimulated B cells and supporting the differentiation of ISC. To examine the role of T supt in B cell activation and the progression through the cell cycle, T cell- and monocyte-depleted B cells were stimulated with formalinized Cowan I strain Staphylococcus aureus (SA), and the percentages of cells in G1, S, and G2 + M were determined by acridine orange staining and analysis. In all experiments, a similar percentage of cells entered G1 during the first 24 to 36 hr of culture when stimulated with SA or SA + T supt. Similar results were seen when B cell activation was analyzed by acquisition of a number of other markers of cell activation. Analysis of cell cycle progression with mithramycin staining of cellular DNA in the presence or absence of vinblastine to arrest mitosis indicated that SA-activated B cells were able to complete S and divide in the absence of T supt. Although an effect of T supt on the progression of B cells through the S phase was evident during the first cell cycle, the major effect only became apparent after the first round of cell division. Although T supt was not necessary for initial B cell activation, T cell influences were absolutely necessary for the differentiation of ISC. T supt did not need to be present during the initial 24 to 36 hr of incubation to permit subsequent generation of ISC. However, when T supt was present initially, an increased number of ISC were produced. Hydroxyurea elimination of cells traversing the G1-S interphase indicated that reception of the differentiation signal occurred before the S phase, but that the generation of ISC required subsequent DNA synthesis and/or cell division. Although precursors of ISC were entirely contained within the population triggered to divide by SA alone, there was no preferential expansion of such precursors as a result of SA stimulation. These results indicate that T cell signals are not absolutely necessary for initial B cell activation and progression through the first cell cycle, although T cell factors promote DNA synthesis by some activated B cells. In contrast, differentiation into ISC is completely dependent on T cell influences.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1984

Regulation of human B cell proliferation by prostaglandin E2.

The role of prostaglandin E2 (PGE2) in the regulation of human B cell proliferation in vitro was examined. Initial studies demonstrated that monocyte (M phi)-mediated suppression of B cell proliferation in Staphylococcus aureus (SA)-stimulated cultures was diminished by indomethacin, and thus it was suggested that cyclooxygenase pathway products of arachidonic acid played a role in the regulation of B cell activation. The possibility that PGE2, one of the major products of this pathway generated by M phi, affected human B cell responses was therefore investigated. PGE2 was found to suppress B cell DNA synthesis and proliferation stimulated by SA in the presence or absence of B cell growth factor (BCGF)-containing T cell supernatants. Suppression was concentration-dependent; significant inhibition was observed in indomethacin-blocked cultures with 10(-10) to 10(-9) M PGE2. In contrast to the effect of PGE2 on SA-induced B cell proliferation, it had minimal effect on pokeweed mitogen (PWM)-stimulated B cell or T cell DNA synthesis. The effect of PGE2 on the generation of BCGF activity from mitogen-stimulated T cells was also examined. PGE2 (10(-7) M) did not inhibit the production of BCGF activity from PWM-stimulated T cells, or from T cells stimulated with the combination of phytohemagglutinin and phorbol myristate acetate. Thus, PGE2 inhibits B cell proliferation in response to SA but not PWM, and has little effect on the production of BCGF by T cells. These results indicate that PGE2 at physiologically relevant concentrations exerts selective regulatory effects on human B cell responses.

Adult↗