Biomedical subjects

J J Mond

Publications and source records attributed to J J Mond.

At least 91 records · Page 5Linked to original sources

PubMed1988

Examination of the inhibitory and stimulatory effects of IFN-alpha, -beta, and -gamma on human B-cell proliferation induced by various B-cell mitogens.

In order to compare the actions of interferons on the various pathways leading to human B-cell activation, we examined the effects of alpha-interferon (INF-alpha), beta-interferon (INF-beta), and gamma-interferon (INF-gamma) on B-cell responses to mitogenic stimuli which differ in their mode of B-cell stimulation. Utilizing highly purified small, dense peripheral blood B-cells or splenic lymphocytes, we demonstrate that (i) INF-alpha, -beta, and -gamma enhance human B-cell proliferation induced by cross-linking of surface Ig with either SAC or anti-mu in a dose-dependent fashion, analogous to and with a magnitude equal to or greater than that seen with human B-cell growth factor; (ii) INF-alpha and -beta but not IFN-gamma inhibit phorbol myristate acetate-mediated B-cell mitogenesis, again in a dose-dependent manner; and (iii) IFN-gamma does not effect B-cell cytoplasmic calcium ([Ca2+]i) influx, either in the resting state or following stimulation with anti-mu, making it unlikely that IFN-gamma exerts its stimulatory effects on B-cell function through changes in [Ca2+]i. Taken together, these findings suggest that all three types of interferons may have important immunoregulatory roles in B-cell activity, and that their ability to enhance or suppress B-cell activation depends on the nature of the mitogenic stimulus.

B-Lymphocytes↗

PubMed1988

The nuclear matrix protein, numatrin (B23), is associated with growth factor-induced mitogenesis in Swiss 3T3 fibroblasts and with T lymphocyte proliferation stimulated by lectins and anti-T cell antigen receptor antibody.

Numatrin is a tightly bound nuclear matrix protein (40 kD/pI-5) whose synthesis is markedly and promptly increased in association with cellular commitment for mitogenesis in B lymphocytes. (Feuerstein, N., and J.J. Mond. 1987. J. Biol. Chem. 262:11389-11397). To study whether this event is exclusively associated with proliferation of B lymphocytes, we examined the synthesis of numatrin in T lymphocytes (murine and human) activated by lectins or by anti-T cell antigen receptor monoclonal antibody and in Swiss 3T3 fibroblasts stimulated by growth factors. We showed a close correlation between induction of DNA synthesis and induction of numatrin synthesis in T lymphocytes stimulated by concanavalin A, anti-T cell antigen receptor monoclonal antibody, and IL-2 in murine T cells. Similar results were observed in Swiss 3T3 fibroblasts, thus only combinations of growth factors (insulin/EGF or insulin/B subunit of cholera toxin) or serum, which induced a significant increase in DNA synthesis, were also associated with a significant increase in synthesis of numatrin. Similar to B cells, the increase in numatrin synthesis in fibroblasts was found to occur at early G1 phase. The calcium ionophores, A23187 and ionomycin, previously shown to induce an increase in c-myc and c-fos mRNA levels in fibroblasts, induced a marked increase in the synthesis of a nuclear protein at 80 kD/pI-5 but failed to induce an increase in the synthesis of numatrin indicating that an increase in intracellular Ca++ level is not sufficient for induction of the synthesis of numatrin. This further indicates that the increase in synthesis of numatrin may be more closely correlated with cellular commitment for mitogenesis as compared with other biochemical parameters. Using a polyclonal numatrin antibody we demonstrated that mitogen stimulation is also associated with a marked increase in numatrin abundance, which reached a peak at the onset of S phase and declined at the end of S phase. Evidence is presented to show that numatrin synthesis and abundance is elevated in various lymphoma cell lines. Using indirect immunofluorescence assays we showed that numatrin is abundant in other malignant cells: KB, epidermoid carcinoma, and Hep2 human hepatoma. Immunofluorescence studies further showed that mitogen stimulation of B lymphocytes induced a marked accumulation of numatrin in the nucleoli. This observation is in accord with the recent finding of identity of numatrin with the nucleolar protein B23 (Feuerstein et al. 1988. J. Biol. Chem. 263:10608-10612).(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗

PubMed1987

Glucocorticoids suppress calcium mobilization and phospholipid hydrolysis in anti-Ig antibody-stimulated B cells.

Glucocorticoids have been shown to play a major role in influencing the activation of B lymphocytes. In view of our recent observation that dexamethasone exerts a marked suppressive effect on an early event in B cell activation that is stimulated by anti-Ig antibody, we investigated its activity on other stimuli that induce intracellular events similar to those produced by anti-Ig antibody. Because the intracellular events that occur after B cell stimulation with phorbol myristate acetate and the calcium ionophore A23187 appear to mimic those that occur after B cell stimulation with anti-Ig antibody, we studied whether the cellular responses elicited by these activation stimuli are affected in a similar fashion by dexamethasone. Whereas anti-Ig antibody-stimulated entry of G0 B cells to the G1 and S phase of the cell cycle was markedly suppressed by dexamethasone, phorbol myristate acetate/A23187 stimulation of these events was resistant to dexamethasone. Our finding that anti-Ig-induced cross-linking of B cell surface Ig, as measured by surface Ig capping, was not inhibited by dexamethasone suggested that corticosteroids inhibit anti-Ig-induced B cell proliferation at a step distal to membrane Ig cross-linking and proximal to phosphatidylinositol bisphosphate hydrolysis. This hypothesis is supported by experiments presented in this manuscript which demonstrate that dexamethasone inhibits anti-Ig-stimulated phosphatidylinositol bisphosphate hydrolysis. We also found that dexamethasone markedly inhibited anti-Ig antibody-stimulated increases in intracellular ionized calcium concentrations. This dexamethasone-mediated suppression is time-dependent as it is not seen when B cells are cultured with dexamethasone for less than 6 hr. Our data suggest that the immunomodulatory activity of glucocorticoids is exerted by binding to its nuclear receptor, thereby preventing the generation of second messengers required for cell activation after agonist-receptor interaction.

Animals↗

PubMed1987

Identification of a prominent nuclear protein associated with proliferation of normal and malignant B cells.

Experiments were undertaken to identify nuclear proteins that might be involved in regulation of the mitogenic process in B lymphocytes. Murine splenic B lymphocytes were purified and cultured with anti-Ig insolubilized onto Sepharose (anti-Ig/Sepharose) for 16 hr and labeled with [35S]methionine. Nuclei were isolated and the nuclear proteins were analyzed by two-dimensional gel electrophoresis. Anti-Ig/Sepharose induced a prominent increase in the synthesis and abundance of a 40 kDa/pI 5 nuclear protein (p40/pI-5). Inhibition of anti-Ig/Sepharose-induced mitogenesis by pretreatment of the cells with phorbol-12-myristate-13-acetate was associated with a specific inhibition (63%) of p40/pI-5. Subcellular fractionation experiments showed that p40/pI-5 is not detected in the soluble fraction of resting or activated B cells, indicating that this protein is located exclusively in the nucleus. Analysis of the expression of p40/pI-5 relative the cell cycle showed that the synthesis of this protein was increased during G1 phase and gradually reduced during S phase of the cell cycle. Abundant amounts of p40/pI-5 were also found in the rapidly proliferating B lymphoma cells, WEHI-231, and growth arrest of these cells by anti-mu was found to be associated with a marked inhibition (68%) of this protein. Taken collectively these results suggest that the nuclear protein p40/pI-5 may have an important role in regulation of the proliferation of normal and malignant B lymphocytes.

Animals↗

PubMed1987

"Numatrin," a nuclear matrix protein associated with induction of proliferation in B lymphocytes.

To detect nuclear proteins that might be involved in induction of cellular mitogenesis, we examined the effect of various mitogens on early changes in synthesis of nuclear proteins in murine B lymphocytes. Using two-dimensional gel electrophoresis, we found that activation of B cells by mitogens (anti-immunoglobulin antibody, lipopolysaccharide, phorbol 12-myristate 13-acetate (PMA)/A23187) was associated with a rapid and prominent (5-20-fold) increase in the synthesis of a 40-kDa/pI 5.0 nuclear protein, here termed numatrin. Numatrin was found to be absent from the cytosol (soluble fraction) of resting as well as activated B cells and was markedly resistant to DNase/RNase digestion and 2 N NaCl extraction, indicating that this protein is tightly bound to the nuclear matrix. Kinetic studies showed that the increase in synthesis of numatrin was detected 60-120 min following mitogen activation, reached a peak at 16 h, and declined to almost control level by 48 h, correlating with the peak of cellular DNA synthesis. The increase in synthesis of numatrin in normal B cells was found to be associated exclusively with cellular commitment for mitogenesis because activation of B cells by stimuli such as B cell stimulating factor 1, PMA alone, and calcium ionophore A23187, which do not stimulate an increase in DNA synthesis, also failed to induce an increase in the synthesis of numatrin. Inhibition of anti-Ig-induced proliferation (by PMA pretreatment) was associated with a 63% inhibition in the synthesis of numatrin. Addition of 8-mercaptoguanosine to these PMA-treated cells was associated with restoration of the increase in synthesis of numatrin, concomitant with induction of proliferation. Elevated synthesis of numatrin was also detected in the malignant B lymphoma cells: Raji, BAL-17, and WEHI-231. Taken collectively, these results suggest that numatrin, a tightly bound nuclear matrix protein, is a growth-regulated protein which might have an important role in regulation of cellular mitogenesis in normal and malignant B lymphocytes.

Animals↗

PubMed1987

The Mlsd-defined primary mixed lymphocyte reaction: a composite response to Mlsa and Mlsc determinants.

Considerable disagreement exists among immunologists regarding the polymorphic nature of the murine Mls system. An estimate of the capacity of a given putative Mls allelic gene product expressed on a stimulator population to elicit proliferation of H-2-compatible Mls-disparate unprimed T cells may vary widely among different groups of investigators. This laboratory has shown previously that preactivation of B lymphocytes in a splenocyte stimulator population by exposure to goat anti-mouse IgD (GaMD) before irradiation dramatically enhanced the in vitro presentation not only of the strongly stimulatory (and highly cross-reactive) Mlsa and Mlsd, but also the more poorly stimulatory Mlsc specificity. Therefore, by the use of GaMD-treated splenocytes that optimally present the various Mls non-H-2 stimulatory epitopes, we attempted in this study to obtain a clearer understanding of Mls polymorphism by re-examining the conflicting claims associated with the mixed lymphocyte reaction (MLR) stimulatory capacity of different Mls specificities. Among H-2k responder cells of the Mls null, Mlsa, Mlsb, or Mlsd genotypes, only T cells from Mlsd-bearing CBA/J mice did not respond to Mlsc determinants present on GaMD-treated C3H/HeJ stimulator cells. Crossing CBA/J with an Mlsc-responsive mouse strain yielded an F1 animal in which nonresponsiveness to Mlsc was dominant. Although Mlsa (AKR/J) and Mlsc (C3H/HeJ) parental T cells both proliferated vigorously to Mlsd (CBA/J) stimulator cells, the Mlsa/c (AKR X C3H)F1 T cells responded poorly to GaMD-treated Mlsd stimulator cells. In addition, Mlsd (CBA/J) T cells were nonresponsive to Mlsa (AKR/J), Mlsc (C3H/HeJ), and Mlsa/c (AKR X C3H)F1 GaMD-treated stimulator cells. Because Mlsa (AKR/J) and Mlsc (C3H/HeJ) specificities are mutually stimulatory, at least limited polymorphism must exist in the Mls system. However, because Mlsa/c (AKR X C3H) and Mlsd (CBA/J) specificities are mutually nonstimulatory, T cell proliferation in an Mlsd-defined primary MLR is most likely due to a composite response to Mlsa and Mlsc epitopes present on CBA/J stimulator cells.

Alleles↗

PubMed1987

Comparison of the calcium requirement for the induction and maintenance of B cell class II molecule expression and for B cell proliferation stimulated by mitogens and purified growth factors.

As an important intracellular second-messenger, the concentration of calcium in the cytosol [Ca+2]i influences diverse cellular activities. To investigate the calcium requirement for distinct phases of B cell activation, we studied the effect of altering the quantity of extracellular calcium on the induction of increased B cell MHC class II molecule (Ia) expression and DNA synthesis by different B cell mitogens. During short-term cultures (less than 24 hr), the induction of class II molecules by anti-immunoglobulin (anti-Ig) and calcium ionophore were dependent on the presence of extracellular calcium, whereas activation induced by B cell stimulation factor-1 (BSF-1) was minimally dependent on extracellular calcium, and that induced by LPS was independent of it. During longer-term cultures (i.e., greater than 24 hr), the heightened class II molecule expression that was induced by all of the B cell mitogens used was significantly compromised by depletion of extracellular free calcium. Although the anti-Ig-stimulated increase in expression of Ia could be restored by the addition of calcium to the medium at 12 hr, it could not be restored when the addition of calcium was delayed to 24 hr after the onset of culture. This was in marked contrast to the finding that BSF-1-stimulated B cell responses which were suppressed after 24 hr of culture in the presence of EGTA could be restored by the addition of calcium. Activation of B cells along the pathway leading to DNA synthesis demonstrated a requirement for extracellular calcium which was greater than that required for induction of MHC class II molecule expression. Thus, LPS-stimulated size increases of B cells after 12 hr of culture was dependent on extracellular calcium while its induction of MHC class II molecule expression was independent of extracellular calcium at this early time point. These observations indicate that the extracellular calcium requirement for B cell activation is dependent both on the activation pathway utilized by the mitogenic signal and on the duration of cell activation. Furthermore, they demonstrate that B cell stimuli that can initiate B cell activation in the relative absence of extracellular calcium may require extracellular calcium for maintenance of this activational state.

Animals↗

PubMed1987

Regulation of the in vitro presentation of minor lymphocyte stimulating determinants by major histocompatibility complex-encoded immune response genes.

Activation of murine B lymphocytes in a splenocyte stimulator population with affinity-purified goat anti-mouse IgD (G alpha M delta) antibody was previously shown by this laboratory to enhance the presentation of strongly stimulatory major histocompatibility complex (MHC) and minor lymphocyte-stimulating (Mlsa,d) determinants in a primary mixed lymphocyte reaction. In the present study, the G alpha M delta treatment of murine splenocytes was employed to enhance the detection of the weakly stimulatory non-MHC Mlsc determinant in order to study the role the MHC might play as a restricting element for the recognition of these minor antigens in a primary mixed lymphocyte reaction. Indeed, enhanced T cell proliferation to Mlsc determinants presented on G alpha M delta-treated splenocytes was observed when the responder and activated H-2-compatible stimulator cell shared certain MHC haplotypes. High responsiveness was associated with the H-2a,k,j,p haplotypes, intermediate responsiveness was associated with the H-2f,g haplotypes and low responsiveness was associated with the H-2b,s haplotypes. (Low X high responder)F1 T cells preferentially responded to the Mlsc determinants presented on G alpha M delta-treated stimulator cells of the F1 or parental high responder H-2 haplotype. When mitomycin C instead of irradiation was used to inactivate normal (non-IgD-treated) splenocytes, a similar preferential response of T cells to Mlsc determinants presented on stimulator cells of a high responder H-2 haplotype was also observed. The inability of G alpha M delta-treated splenocytes of the low responder haplotype to elicit substantial levels of T cell proliferation across an Mlsc difference could not be attributed to the failure of these stimulator cells to become activated by the anti-Ig antibody. In addition, co-culture experiments could not identify the poor T cell response to Mlsc determinants presented on certain MHC haplotypes as being caused by the induction of nonspecific suppressor cells. Presentation of Mlsc determinants caused by transgene product complementation was detectable in F1 mice derived by crossing one parent that had the Mlsc non-MHC genes and a poorly permissive H-2 haplotype with a parent that expressed a permissive H-2 haplotype but lacked the Mlsc non-MHC genes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1987

Synergistic effects of the xid gene in X chromosome congenic mice. I. Inability of C3.CBA/N mice to respond to thymus-dependent antigens in adoptive transfer assays.

The xid gene, which causes a B lymphocyte immune defect in CBA/N mice, has been bred onto the C3H/HeN background. The resulting X chromosome congenic mice (C3.CBA/N) exhibit immunologic defects that are much more profound than the defect exhibited by CBA/N mice; thus, the B cells from C3.CBA/N mice not only fail to respond to thymus-independent (TI) type 2 antigens such as TNP-Ficoll, but they fail to respond in vitro to TI-type 1 antigens such as TNP-Brucella abortus (BA) and B cell mitogens such as LPS and Nocardia water-soluble mitogen. In this paper we show that the synergistic defect seen in C3.CBA/N B cells is also elicited in adoptive transfer assays to thymus-dependent (TD) antigens such as TNP-KLH and PC-KLH, antigens to which both parental strains respond. Thus, the secondary adoptive transfer response of C3.CBA/N spleen cells is generally less than 5% of the immune response produced by CBA/N or C3H/HeN spleen cells. This synergistic defect is restricted to the C3.CBA/N B cells, since C3.CBA/N T cells can provide help to CBA/N B cells that is equivalent to the help obtained with CBA/N T cells. The low responsiveness of C3.CBA/N spleen cells to TD antigens, which is elicited in adoptive transfer assays, is not seen when the intact animal is immunized with antigen in CFA; this, intact C3.CBA/N mice produce anti-PC-KLH and anti-TNP-KLH responses only slightly lower than the responses of CBA/N mice to these same antigens. In contrast, when these mice are immunized with phenol-extracted LPS, a TI-type 1 antigen, their antibody responses are severely depressed. These data suggest that under conditions in which T cell help may be limiting or in which the intact physiology of the T and B cells has been disrupted, C3.CBA/N B cells demonstrate profound immunologic impairment; however, when adequate T cell help is available and the splenic architecture is not disrupted, their immune responses appear to progress in a normal fashion.

Animals↗

PubMed1987

B-cell activation stimulated by monoclonal anti-Lyb2.1 antibody is mediated through a receptor distinct from the BSF-1 receptor.

The experiments in this paper demonstrate that monoclonal anti-Lyb2.1 antibody enhances the proliferative response of anti-immunoglobulin (anti-Ig)-stimulated but not of dextran sulfate-stimulated B cells. The magnitude of this enhanced B-cell proliferation is comparable to that induced by BSF-1 on anti-Ig-stimulated cells. The ability of this antibody to enhance B-cell proliferation does not result from its ability to neutralize the suppressive effects on B-cell activation that is mediated by the Fc fragment of anti-Ig antibody as it is equally as effective in enhancing B-cell proliferative responses stimulated by F(ab')2 fragments of anti-Ig. BSF-1 and Anti-Lyb2.1 appear to stimulate nonoverlapping pathways leading to B-cell activation since the enhanced responses induced by the combination of BSF-1 and anti-Lyb2.1 on anti-Ig-stimulated cells are additive even when maximum quantities of these activators are employed. There is also a marked difference in their activity on T cells; while BSF-1 can enhance T-cell proliferation in synergy with phorbol ester, anti-Lyb2.1 is ineffective in this regard. These data, while consistent with the suggestion that the Lyb2 surface determinant on B cells may be involved in B-cell activation, indicate that it is distinct from the receptors for BSF-1 or BCGF-II.

Animals↗

PubMed1987

B-lymphocyte activation mediated by anti-immunoglobulin antibody in the absence of protein kinase C.

B-cell activation induced by crosslinking of surface immunoglobulin is known to stimulate hydrolysis of phosphatidylinositol to diacylglycerol and inositol trisphosphate. We now provide evidence that alternative pathways of activation may also be recruited during such activation. We utilized depletion of protein kinase C activity to determine whether this enzyme is required under all conditions for anti-immunoglobulin-stimulated B-cell activation. Although anti-immunoglobulin does not induce B-cell proliferation in protein kinase C-depleted cells, it stimulates an earlier event in B-cell activation as reflected by its ability to enhance the expression of major histocompatibility complex-encoded class II molecules. Furthermore, the ribonucleoside 8-mercaptoguanosine restores the ability of anti-immunoglobulin to induce B-cell proliferation in protein kinase C-depleted cells. This restoration is also demonstrated by an enhancement of synthesis of a nuclear protein that we find is increased during B-cell mitogenesis. These results indicate that B-cell activation stimulated by anti-immunoglobulin may recruit pathways in addition to the one dependent on protein kinase C.

Animals↗

PubMed1987

A role for IFN-gamma and NK cells in immune responses to T cell-regulated antigens types 1 and 2.

Responses to antigens that have been previously recognized as T cell-independent are now known to be dependent on some form of T-cell (or T cell-derived) help. This T-cell dependency, however, can be most easily noted when responses to small resting B cells are examined, since responses of larger, size-separated B cells to TNP-Ficoll require little if any T-cell help. The type of ancillary "help" that is required for the responses to type 1 and type 2 antigens exhibits certain similarities as well as differences. Thus, responses to both of these antigens can be stimulated in the presence of L3T4- or L3T4+ cells as well as in the presence of IL2. However, while the presence of IFN-gamma may be significantly inhibitory for the responses to the type 2 antigen TNP-Ficoll, they do not appear to influence the response to the type 1 antigen TNP-BA. Furthermore, while vigorous elimination of NK cell activity from purified B-cell populations enhances the response to TNP-Ficoll, it has no discernible effect on the response to TNP-BA. These results suggest that determination of type 1 and type 2 antigens may be made not only based on the characteristics of the carrier molecule but also on the nature of ancillary help that needs to be provided for these antigens to stimulate optimal responses. Type 1 antigens have polyclonal B-cell activating properties and stimulate responses which are not influenced by IFN-gamma, type 2 antigens have no polyclonal B-cell activating properties and stimulate responses which can be influenced by IFN-gamma.

Animals↗

PubMed1986

Interferon-gamma suppresses B cell stimulation factor (BSF-1) induction of class II MHC determinants on B cells.

The data presented in this manuscript extend our previous observations that recombinant interferon-gamma (reIFN-gamma) can suppress anti-immunoglobulin (anti-Ig)-stimulated B cell proliferation, and demonstrate that reIFN-gamma can also suppress B cell stimulation factor type 1 (BSF-1)-stimulated increases in expression of MHC class II molecules (Ia) on B cells. This suppression is most effective when relatively low concentrations of BSF-1 are employed, but is still very substantial even when optimal concentrations of BSF-1 were used. This suppression is also observed when size-separated small B cells which are devoid of detectable macrophages or NK cells are cultured with BSF-1 and reIFN-gamma, thus suggesting that IFN-gamma-mediated inhibition is a consequence of a direct effect on the B cells. Incubation of B cells with reIFN-gamma for 24 hr before their culture with BSF-1 did not prevent BSF-1-stimulated increases in sIa. This finding supports the contention that the effect of IFN-gamma is not mediated via the stimulation of "suppressor" influences in these cell cultures. The inhibition of B cell activation by IFN-gamma occurs within the first 3 hr after the onset of culture, as demonstrated by the inability of antibody to IFN-gamma to totally reverse the IFN-gamma-mediated suppressive effects on B cell proliferation if it is added later than 3 hr after the onset of culture. These results suggest a role for IFN-gamma in down-regulating the ability of B cells to function as antigen-presenting cells in non-cognate T cell-dependent responses.

Animals↗

PubMed1986

Production of BSF-1 during an in vivo, T-dependent immune response.

BSF-1, a cytokine produced by some T lymphocyte tumors, has been shown to act with anti-Ig antibodies to stimulate B lymphocyte proliferation, to independently induce resting B lymphocytes to increase their expression of surface Ia antigen, and to induce some activated B lymphocytes to differentiate into IgG1- or IgE-secreting cells. To determine whether BSF-1 might be secreted by normal lymphoid cells in the course of a physiologic immune response, BALB/c mice were injected with an affinity-purified goat antibody to mouse IgD (GaM delta), which induces the generation of a large, polyclonal T-dependent IgG1 response; 4-hr culture supernatants of spleen cells from these mice were prepared, and these supernatants were assayed for BSF-1 activity by analyzing their ability to induce BALB/c nu/nu spleen cells to increase their expression of cell surface Ia in vitro. Culture supernatants of unfractionated spleen cells removed from mice 4 to 8 days after GaM delta antibody injection induced substantial increases in B lymphocyte surface Ia expression; these increases were blocked by a monoclonal anti-BSF-1 antibody. Culture supernatants of spleen cells from untreated BALB/c mice or from untreated or GaM delta antibody-treated BALB/c nu/nu mice induced small to moderate increases in B cell surface Ia expression, and GaM delta antibody itself induced large increases in B cell surface Ia expression; however, these increases were not significantly blocked by a monoclonal anti-BSF-1 antibody. A culture supernatant of T cell-enriched spleen cells from untreated mice induced small increases in B cell surface Ia expression that were inhibited by anti-BSF-1 antibody, as was the larger increase in B cell Ia expression induced by a culture supernatant of T cell-enriched spleen cells from mice sacrificed 3 days after GaM delta injection. On the other hand, T cell-depleted spleen cells from BALB/c mice injected with GaM delta antibody 7 days before sacrifice failed to generate culture supernatants with BSF-1 activity. Supernatants prepared from spleen cells taken from untreated mice or mice treated with GaM delta antibody 1 to 3 days before sacrifice did not block the ability of purified BSF-1 to induce an increase in B cell surface Ia expression, and thus did not contain inhibitors of BSF-1 activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1986

In vivo and in vitro expression of an interleukin 2 receptor by murine B and T lymphocytes.

Interleukin 2 (IL 2), which is well established to be a T cell growth factor, has more recently been shown to stimulate B lymphocyte growth and differentiation in vitro. Responsiveness of B and T cells to IL 2 has been associated with expression of a cell membrane IL 2 receptor (IL 2R). To investigate the role of IL 2 in B cell growth and differentiation in vivo, a system was used in which the injection of mice with a goat antibody to mouse IgD (GaM delta) induces polyclonal T-independent B cell proliferation first, and later induces polyclonal T-dependent B cell proliferation and IgG secretion. IL 2R expression by splenic B and T lymphocytes from GaM delta injected mice was studied by a dual label immunofluorescence technique. Although GaM delta was found to be a strong inducer of B cell IL 2R expression in vitro, even in serum-free medium, and stimulated up to 50% of splenic T cells to express considerable quantities of IL 2R in vivo, it failed to induce more than minimal B cell IL 2R expression in vivo. Concanavalin A and bacterial lipid A also induced B cells to express IL 2R to a much greater extent in vitro than in vivo. Although these agents and GaM delta acted synergistically to stimulate B cell IL 2R expression both in vitro and in vivo, a single agent induced B cell IL 2R expression to a considerably greater extent in vitro than did all three agents acting together in vivo. In vitro GaM delta-induced B cell IL 2R expression was not suppressed by inclusion of IL 2 in the culture medium but was suppressed by the presence of 10% normal mouse serum or plasma. These observations suggest that polyclonal T-dependent B cell proliferation and antibody secretion may not require an interaction between B cells and IL 2; the in vivo environment may downregulate IL 2R expression by B cells: and in vivo B cell IL 2R expression and consequently, induction of B cell responsiveness to IL 2, may require stimuli beyond those sufficient to induce B cell IL 2R expression and IL 2 responsiveness in vitro.

Animals↗

PubMed1986

Enhancement by monoclonal anti-Lyb-2 antibody of antigen-specific B lymphocyte expansion stimulated by TNP-Ficoll and T lymphocyte-derived factors.

By using antigen-specific populations of B cells (TNP-ABC) we have demonstrated that the type-2 antigen TNP-Ficoll was capable of initiating B cell proliferation only in the presence of T cell-derived factors. Monoclonal-anti-Lyb-2.1 antibody acted synergistically with a T cell-derived supernatant, as well as with B cell-stimulating factor (BSF-1) to enhance the level of B cell expansion obtained in this in vitro system. This effect of anti-Lyb-2.1 mAB was observed at each day of the antigen-driven B cell expansion and was seen only with B cells purified from strains expressing the Lyb-2.1 allele. The epitope density of hapten on the Ficoll plays a critical role in this process, because Ficoll that is haptenated with low density of hapten was not found to be stimulatory. These results suggest that the Lyb-2 surface molecule influences the antigen-driven B cell growth that is stimulated by type 2 antigens and BSF-1.

Animals↗

PubMed1986

Interferon-gamma inhibits the action of B cell stimulatory factor (BSF)-1 on resting B cells.

B cell stimulatory factor-1 (BSF-1) stimulates resting B cells to increase in volume and prepares these cells to enter the S phase in response to anti-IgM and other B cell mitogens. Interferon-gamma (IFN-gamma) blocks both the volume enlargement and preparation for DNA synthesis caused by BSF-1, although it has little effect on B cells already stimulated by BSF-1. The capacity of IFN-gamma to inhibit the action of BSF-1 on resting B cells suggests a mutual regulatory interaction between these two T cell-derived products.

Animals↗

PubMed1986

B cell stimulatory factor 1 (BSF-1) prepares resting B cells to enter S phase in response to anti-IgM and lipopolysaccharide.

BSF-1 prepares resting BALB/c, DBA/2, and BDF1 B cells to enter S phase more promptly in response to subsequent culture with anti-IgM-based stimulants. It prepares DBA/2 and BDF1 B cells to respond to LPS, but its preparative effect for LPS responses of BALB/c B cells is both inconstant and meager. Preparation mediated by BSF-1 requires extended contact of B cells with the stimulant for full effect. Half-maximal preparation requires approximately 12 h of contact, as judged by delayed addition of BSF-1 or by inhibition of BSF-1 action with anti-BSF-1 mAbs. BSF-1 preparative action on resting DBA/2 B cells is mimicked by anti-Lyb-2.1 antibody. B cell blasts prepared by culture with BSF-1 and anti-IgM show modest responses to high concentrations of BSF-1; large B cells directly isolated from the spleen are not stimulated to enter S phase by BSF-1. These results lead us to conclude that BSF-1 functions principally as an activation factor for resting B cells.

Animals↗