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1.
The 24-hr culture supernatant of Con A-activated spleen cells (SN) contains helper factors that enable maturation to high-rate polyclonal Ig secretion and enhance proliferation in cultures of mouse B cells activated with the F(ab')2 fragment of class-specific rabbit antimouse IgM antibody (anti-Ig). When interleukin 2 (IL 2), also called T cell growth factor, is removed from SN by absorption with an IL 2-dependent cell line at either 4 degrees C or 37 degrees C, all the helper activity for anti-Ig-activated B cells is also removed. Partial removal of IL 2 results in partial removal of helper activity for B cells. However, the IL 2-depleted SN appears to contain another helper factor, TRF, that enables anti-Ig-activated B cell cultures to mature to high-rate Ig secretion. This TRF activity is revealed by adding purified human IL 2 or an IL 2-containing supernatant of a cloned, lectin-activated T cell hybridoma line (FS6-14.13) to Il 2-depleted SN, which restores the polyclonal antibody response to anti-Ig. The hybridoma supernatant by itself supports proliferation of anti-Ig-activated B cell cultures, as measured by an increase in cell number, but not maturation to Ig secretion. This proliferative response is likewise IL 2 dependent, although purified IL 2 with anti-Ig is not sufficient. These experiments define separable combinations of factors acting on anti-Ig-activated B cell cultures, one of which (SN) results in both proliferation and maturation to high-rate Ig secretion, whereas the other (hybridoma supernatant) results in proliferation only. IL 2 appears to be an essential component of both combinations, although the target cell for IL 2 action in this system remains to be determined.  相似文献   

2.
The effects of IL 2 and gamma-IFN on the activation of human B cells was studied with recombinant IL 2 and gamma-IFN. BCDF-responsive B lymphoblastoid cell lines and highly purified human B cells were employed as target B cells. IL 2 or gamma-IFN did not induce any IgG or IgM secretion in the B cell lines CESS and SKW6-CL4, in which IgG and IgM were inducible with conventional T cell factor(s). IL 2 alone did not induce the optimum production of Ig, but did induce proliferation in the SAC-stimulated B cell population. No Leu-1-, Leu-4-, or Leu-7-positive cells were detected in B cell populations that had been stimulated with SAC for 3 days. FACS analysis showed that a portion of the SAC-stimulated B cells (30%) were in the G2 or M stages by IL 2 stimulation. The addition of gamma-IFN together with IL 2 induced IgM and IgG secretion in SAC-stimulated B cells that was comparable with that induced by a conventional T cell factor(s). IL 2 induced proliferation not only in SAC-stimulated B cells but also in an anti-mu-stimulated B cell population. Stimulation of T cell populations with anti-mu and IL 2 did not induce significant proliferation, suggesting the direct effect of IL 2 on B cells. Double staining of anti-mu-stimulated B cells with anti-Ig and anti-Tac antibodies demonstrated that anti-mu stimulation induced an increased expression of Tac antigen on surface Ig-positive B cells. All of these results strongly supported the notion that IL 2 was one of the growth factors for B cells, and gamma-IFN was one of the differentiation factors for B cells.  相似文献   

3.
A human helper T cell clone (d4), which showed its helper effect on the differentiation of both T and B cells, was established by MLC reaction of normal T cells against a B lymphoblastoid cell line (CESS) followed by cloning in the presence of IL2 and x-irradiated CESS and autologous non-T cells. d4 cells helped the induction of cytotoxic T cells against UV-treated CESS cells. Antigen-stimulated d4 cells secreted helper factor(s) involved in the induction of cytotoxic T cells (killer helper factor(s), KHF), and KHF activity could be separated into two fractions, one with the m.w. of 15,000 to 20,000 and the other with the m.w. of 45,000 to 50,000. The factor with 15,000 to 20,000 m.w. showed IL 2 activity; the other factor showed gamma-interferon activity without IL 2 activity, suggesting that both IL 2 and gamma-interferon exerted KHF activity. d4 cells or their culture supernatant showed helper activity in the induction of IgG in a B cell line (CESS). The helper activity of the supernatant (TRF) was absorbed with CESS cells but not with IL 2-dependent CTLL, whereas KHF activity was absorbed with IL 2-dependent CTLL but not with CESS cells. The results showed that TRF and KHF were distinct molecules and a single helper T cell clone could secrete helper factors for both B and T cells.  相似文献   

4.
T lymphocytes are thought to provide "help" for B cells by activating them from the resting state, by secretion of antigen-nonspecific lymphokines that promote B cell differentiation and maturation, and by providing signals that induce isotype switching. To clarify the extent to which these different forms of helper activity could be carried out by individual T cells, we set up cultures in which B cells activated, and were in turn themselves stimulated by, limiting numbers of T cells through differences at the H-2 or Mls loci. At T cell doses at which responses were likely to represent the activity of individual helper T cells (or their immediate clonal progeny), we found that some T cells were able both to produce interleukin 2 (IL-2) and to induce secretion of both IgM and IgG, whereas others induced immunoglobulin (Ig) secretion without detectable IL-2 production, and still others made IL-2 but did not promote antibody secretion. We could not detect B cell stimulatory factor 1 production by alloantigen-stimulated T cells, and the addition of antibodies to B cell stimulatory factor 1 did not prevent Ig production. Two results, however--higher Ig accumulation in those wells that received an IL-2-producing cell, and inhibition by anti-IL-2 receptor antibodies of B cell but not T cell function--are consistent with a direct stimulatory effect of IL-2 on B cells in this system. The pattern of helper functions exhibited by T cells freshly isolated from mice differs from that inferred from studies of cloned lines of T cells in long term cultures.  相似文献   

5.
Circulating mononuclear cells (MNC) from normal donors were examined for lymphocyte proliferation and plasma cell differentiation following stimulation by Fc and Fab fragments or by intact IgG. Lymphocyte differentiation and DNA synthesis were examined as a function of culture duration and concentration of Fc, Fab fragments, and IgG. Plasma cells containing intracytoplasmic Ig were demonstrated by immunofluorescence with a polyvalent antiserum to human immunoglobulin and with specific antisera (anti-mu, -gamma, -alpha, -delta, -kappa, and -lambda chains). DNA synthesis of mononuclear cells cultures was analyzed by measuring [3H]thymidine incorporation. The results indicated that only the Fc fragments are able to induce the differentiation of B cells. The polyclonal plasma cell response to Fc fragments was dose dependent, peaked on the sixth day of culture, and was isotypically diverse (IgM greater than IgA greater than IgG). This activity requires the presence of T helper cells and monocytes. In contrast, the Fc fragments were unable to induce a proliferative response.  相似文献   

6.
Mouse B cells are stimulated to proliferate by Fab'2 fragments of rabbit anti-mouse Ig antibodies. Proliferation is inhibited, however, in the presence of IgG anti-mouse Ig. We have previously shown that this inhibition is mediated by binding of the IgG anti-Ig to receptors for Fc gamma R on B cells. This report describes conditions under which IgG anti-mu or anti-delta will induce proliferation despite Fc gamma R engagement. Culture supernatants of Con A-stimulated, Il-4-secreting Th cell lines, but not of Il-2-secreting Th cell lines, will co-stimulate with IgG anti-Ig to induce small B cells to incorporate [3H]TdR. This co-mitogenic activity is inhibitable by anti-IL-4 antibodies and can also be induced by Il-4 affinity purified from the T cell supernatants or by supernatants containing rIl-4. B cells precultured with Il-4 for 18 h, while still expressing normal levels of Fc gamma R, also proliferate to IgG anti-Ig. We have previously shown that Fc gamma R-mIg cross-linking will inhibit mIg-dependent increases in c-myc mRNA levels. We investigated whether Il-4 allows B cells to respond to IgG anti-Ig by elevating c-myc. The data show that Il-4 has little effect on c-myc mRNA levels in either IgG or Fab'2 anti-Ig-containing cultures.  相似文献   

7.
We analyzed the regulation of immunoglobulin (Ig) production in short-term cultures of human (rib) bone marrow cells. In contrast to blood or tonsil cell cultures, large quantities of IgG and IgA, but not IgM, were secreted by unstimulated marrow cells. The addition of pokeweed mitogen or phytohemagglutinin resulted in the suppression of this Ig secretion. Both mitogens induced the production of high levels of interleukin 2 (IL 2) in marrow cultures, and the addition of IL 2 alone mimicked the suppressive effect of mitogens. Incubation of marrow cells with Epstein Barr virus resulted in enhanced Ig secretion, primarily of the IgM isotype. The addition of mitogen or IL 2 suppressed Ig production in these cultures as well. The mitogen-induced suppression of Ig secretion in stimulated or unstimulated marrow cultures was inhibited by the monoclonal anti-TAC (IL 2 receptor) antibody. Cell separation experiments indicated that the induction of suppressor activity in marrow cultures involved two distinct populations of marrow-resident T lineage cells. The first population responds to activation by mitogens with the production of IL 2. This population has a surface phenotype appropriate for helper T cells. The second T cell population expresses T8 and TAC determinants. These cells acquire suppressor cell activity after exposure to IL 2. The expression of suppressor function does not require additional (e.g., mitogenic) activation signals. The IL 2-dependent marrow suppressor T cells represent a newly recognized T lymphocyte subset. The regulatory pathway delineated may be important for the regulation of antibody formation in bone marrow, the major site of Ig production in man.  相似文献   

8.
The ability of PPD to induce Ig production in human PBL was investigated. PPD proved to be a good B cell activator for inducing polyclonal Ig production in PBL from healthy Japanese. Comparative studies of this response with PWM-induced Ig production showed that the cellular mechanisms involved in the two responses were different. First, PBL from an atypical individual with a deficient IgM production to PWM responded normally to PPD with IgM production as well as IgG production. Secondly, in IgG production, the effects of the two mitogens (PPDand PWM) were additive. An analysis of the cellular requirements in PPD-induced Ig production clearly demonstrated that T cells played a role in this response as well as in the PWM-induced response. However, the head-to-head comparative study on the titration curves of helper T cells in the two responses showed that PWM-induced helper activity was 2 to 5 times more effective than PPD-induced helper activity. Moreover, PPD-induced helper activity was shown to be more sensitive to ionizing radiation than was PWM-induced helper activity. Thus, this system of PPD-induced Ig production may provide a useful tool for understanding the human antibody production system as well as the PWM-induced response.  相似文献   

9.
It has recently been demonstrated that there are at least two separate pathways by which a single keyhole limpet hemocyanin (KLH) reactive T cell clone can induce B cell differentiation. With the use of the high-dose antigen-driven system (10 micrograms/ml trinitrophenyl (TNP)-KLH), a KLH-specific T cell clone was able to induce a primary anti-TNP response in unprimed B cells. In the presence of aliquots of the same T cell clone, a low-dose of antigen (5 X 10(-2) micrograms/ml TNP-KLH) induced an immunoglobulin (Ig)G response in primed B cells. It has also been demonstrated that there are variant subclones of such KLH-specific helper T cell clones that are unable to provide antigen-specific help in the presence of low-dose antigen but maintain the high-dose antigen-driven helper response. This study was undertaken to investigate whether interleukin 2 (IL 2) had some activity in the low-dose, antigen-driven response induced by the T cell clone. With the use of a variant T cell clone (which lost low-dose, antigen-driven helper activity), it was demonstrated that IL 2 was capable of reconstituting the low-dose, antigen-driven helper activity. To investigate whether accessory cells were required in this system, we removed the adherent cell population from the primed spleen cells added to culture. Interestingly, removal of the G10-adherent cells eliminated the low-dose, antigen-driven response induced by IL 2. Additionally by add-back experiments, we were able to demonstrate that the necessary adherent cell population did not require major histocompatibility complex (MHC) restriction for reconstitution of the IL 2-dependent, low-dose, antigen-driven response. Furthermore, 1% concanavalin A (Con A) supernatant (Sn), but not interleukin 1 (IL 1), could replace this adherent cell function. These data suggest that in this system, IL 2 bypasses the MHC-restricted interaction between T cells and antigen-charged adherent cells; B cells can present antigen to cloned helper T cells efficiently for primary responses but need an added factor(s) to induce IgG production; and adherent cells are essential for IgG production in primed B cells, possibly through the release of soluble factor(s) included in Con A Sn.  相似文献   

10.
In a Th cell-dependent antibody response, the Th act on B cells partly via a helper activity that is cell contact-dependent and cyclosporine A (CsA)-resistant. This activity seems to be required to induce responsiveness of the B cells toward T cell-derived soluble factors (cytokines) generally believed to be essential for B cell proliferation as well as for Ig secretion. In our study, we have investigated a system in which human B cells are stimulated by mutant EL-4 thymoma cells of mouse origin. It was found that human B cells proliferate and secrete Ig (either 1) in the presence of EL-4 cells plus human T cell supernatant (T-SUP), or 2) in the presence of EL-4 cells alone which have been induced with PMA or IL-1. The first situation conformed to the known synergy between CsA-resistant Th signal and cytokines. However, the B response due to PMA-induced EL-4 cells was special. The PMA-inducible helper activity was CsA-sensitive at the same CsA concentration that inhibited IL-2 secretion of EL-4 cells, but the murine factors in EL-4 supernatant had no effect on human B cells; the helper effect did not occur across a semipermeable membrane. Any contribution of soluble factors from contaminating human T cells was ruled out by adding single human B cells by flow microfluorimetry to cultures with EL-4 cells and PMA. Such B cells generated clonal IgM, IgG, and/or IgA responses. CsA, thus, interfered with some cell contact-mediated signal. However, CsA did not reduce the amount of LFA-1 molecules on EL-4 cells. In conclusion, EL-4 cells can induce proliferation and differentiation of human B cells in a soluble factor-independent manner, via CsA-resistant and CsA-sensitive helper activities. This may represent an alternative pathway of B cell activation.  相似文献   

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