Participation of Interleukins in Synergistic Effect of Bu-WSA on Concanavalin A-Induced DNA Synthesis in Mouse Splenic Lymphocytes

Butanol-extracted water-soluble adjuvant (Bu-WSA) obtained from Bacterionema matruchotii was mitogenic to murine splenic B lymphocytes, but not T lymphocytes. When murine splenic cells were cultured in the presence of Bu-WSA and concanavalin A (Con A) together, [3H]thymidine uptake of the culture cells synergically increased. The mechanism of the synergy of Con A and Bu-WSA and the participation of interleukin (IL) 1 and 2 in the synergy were studied. The proliferation cells in the synergy were Lyt-1+23- lymphocytes. Ia-positive accessory cells were required for the response. When separated cell populations and Marbrook-type culture vessels were used, a mixed cell population of T lymphocytes and B lymphocytes or macrophages (M phi) produced some active factor(s) after co-stimulation by Con A and Bu-WSA, and the factors enhanced DNA synthesis of another Con A-activated T lymphocyte population. Supernatants obtained from the spleen cell cultures or the mixed cell cultures with T lymphocytes and M phi in the presence of Con A and Bu-WSA contained greater amounts of IL-1 and IL-2 than those from cultures containing Con A or Bu-WSA alone. An addition of exogenous IL-1 or IL-2 to spleen cell cultures with Con A resulted in a proliferative response like that obtained through co-stimulation by Con A and Bu-WSA. These results suggest that the synergistic effect of Con A and Bu-WSA on the proliferative response in murine splenic cells is sustained by the enhancement of production of these T-lymphocyte growth factors.     

The roles of interleukins in the synergistic effect of B-cell mitogens with concanavalin A on hydrocortisone-resistant thymic cell proliferation.

Investigations were made to determine the roles of interleukin (IL)-1 and IL-2 in the synergistic enhancement of DNA synthesis by concanavalin A (Con A) and bacterial lipopolysaccharide (LPS) or butanol-extracted water-soluble adjuvant (Bu-WSA) from Bacterionema matruchotii in cultures of thymic cells taken from hydrocortisone (HC)-treated C3H/HeN (LPS-responsive) and C3H/HeJ (LPS-non-responsive) mice. When the C3H/HeNCrj cells were cultured in the presence of Con A and LPS or Bu-WSA together, [3H]thymidine [( 3H]TdR) uptake of the cells was enhanced synergistically in comparison with those cultured with either one of the mitogens alone. The synergistic effect on thymic cells was dependent on Ia-positive accessory cells, since a previous treatment of the cells with anti-Iak serum and complement inhibited the response, and the inhibition could be relieved by the addition of either purified peritoneal exudate macrophages (Mø) or splenic B lymphocytes. The co-stimulation of cells with Con A and LPS or Bu-WSA also enhanced their production and release of thymic cell growth factor(s) into the culture medium. The amounts of IL-1 and IL-2 in the culture supernatants were sufficiently high to explain the activities of the growth factor(s). On the other hand, enhanced IL-2 production without significant increase in IL-1 was seen in the co-cultures of anti-Ia+ cell deprived thymic cells and purified splenic B cells prepared from C3H/HeNCrj mice in the presence of Con A and LPS or Bu-WSA, and it was seen in the cultures of C3H/HeJ thymic cells with Con A and LPS. These results suggest that the synergistic effect of Con A and LPS or Bu-WSA on the proliferative response of HC-treated thymic cells is mainly due to the enhanced production of IL-2 and its action to increase cell growth, and there are two pathways by which the enhancement of IL-2 production by Con A and LPS or Bu-WSA can occur: an IL-1-dependent pathway, or an IL-1-independent one.     

A suppressor B lymphocyte inhibiting IL-2 consumption in spleen cell cultures from Mycobacterium bovis BCG-infected mice.

In concanavalin A (Con A)-activated spleen cell (SC) cultures from normal C57BL/6 mice, the production of IL-2 peaked at 18-20 hr after initiation of cultures and declined rapidly during the next 24 hr, the decline of IL-2 activity being due, at least in part, to its utilization by the Con A-induced IL-2 receptor cells. In Con A-activated SC from BCG-infected mice, significant levels of IL-2 activity persisted in the 48-hr and 72-hr culture supernatants, a situation which seemed to be related to the depressed capacity of infected splenocytes to acquire IL-2 receptors. In cell mixing experiments, SC from infected mice actively depressed the utilization of IL-2 by Con A-activated normal SC, thus indicating that suppressor cells can down-regulate IL-2 responsiveness. These suppressor cells may belong to the B-cell lineage since they possessed the Thy-1-, sIg+ and FcR+ phenotype.     

Proliferation of an athymic mouse-derived T-cell clone on thymic stromal cells with interleukin-2.

An athymic mouse-derived CD4+8+ T-cell clone, N-9F, was established. It expresses both full length gamma and delta T-cell receptor (TcR) mRNA. N-9F clone was not maintained by interleukin-2 (IL-2) alone but required another soluble mediator(s), contained in concanavalin A-stimulated splenocyte culture supernatant, for its proliferation. By culturing N-9F on thymic stromal cells, [3H]thymidine incorporation was retained and expression of IL-2 receptor (IL-2R) was induced. This phenomenon was also observed on thymic stromal cells from H-2 allogeneic mice, but not on other cell types such as splenic adherent cells or fibroblasts. After addition of recombinant IL-2 into the N-9F culture with thymic stromal cells, N-9F showed enhanced IL-2R expression and greatly proliferated. The inability to detect any soluble factors in thymic stromal cell culture supernatant suggests that this interaction is mediated by direct cell contact between T and thymic stromal cells. Because a CD2-negative subclone, N-9.23, also proliferated on thymic stromal cells, there might exist a type of molecule other than CD2/LFA3 or TcR/MHC involved with thymic stroma and T-lymphocyte interaction.     

IL-2 and IL-4 can co-modulate the generation of cytotoxic T cells through CD8- CD4- splenic lymphocytes.

Following activation with concanavalin A (Con A), murine T cells are able to suppress the generation of allospecific cytotoxic T lymphocytes (CTL). We have analysed the phenotype, tissue distribution, and mode of action of these cells in an effort to understand further the regulation of CTL-mediated immunity. The precursors of such cells are rare (1 cell per 70,000 spleen cells being able to suppress the generation of a particular allospecific response), but are much more abundant in the spleen than in the thymus. By the use of cytotoxic antibodies, we have been able to demonstrate that the splenic precursors of such cells are Thy-1.2+, CD4-, CD8- but, following activation with Con A, these cells acquire the CD8 marker. Cellular suppression by these lymphocytes is dramatically increased in the presence of the Th2-derived lymphokine, IL-4, whereas IL-2, the Th1-derived lymphokine, significantly augments the generation of CTL in a mixed lymphocyte culture even though relative suppression is still evident in the presence of Con A-activated lymphocytes. Suppression is not due to overcrowding of a cell culture since adding Con A-activated cells to an A anti-B + C culture often resulted in the suppression of the A anti-B response but not the A anti-C response, or vice versa. Suppression appears to require cellular interaction since supernatants from Con A-activated lymphocytes are unable to mediate suppression. Such cells may play an important intermediate role in homeostasis.     

Unresponsiveness to Con A in spleen cell cultures of M. lepraemurium-infected mice is dependent on a defective expression of high-affinity IL-2 receptors rather than on a lack of IL-2 production.

The production of interleukin-2 (IL-2) by Con A-activated spleen cells (SC) progressively declined and reached negligible values during the course of infection of C57BL/6 mice with Mycobacterium lepraemurium. In addition, the capacity of cultured SC to utilize IL-2 was highly reduced, as demonstrated by the accumulation of IL-2 activity in culture supernatants at 48 and 72 h after Con A activation. The depressed IL-2 utilization started to be observed about 1 to 2 weeks prior to the onset of the depressed IL-2 production and was not reversed by the addition of exogenous IL-2; thus implying that a lack of IL-2 utilization rather than a lack of IL-2 production could be directly responsible for the inhibition of T-cell proliferative responses to Con A in SC cultures of infected mice. The utilization of IL-2 was found to be down-regulated, at least in part, by splenic suppressor cells since, in mixed-culture experiments, SC from infected mice actively depressed the capacity of normal splenocytes to consume IL-2. Finally, the depressed IL-2 utilization would result from a 2- to 3-fold reduction of either or both the density of high-affinity IL-2 receptors and their affinity for IL-2.     

A mechanism of retinoid potentiation of murine T-cell responses: Early upregulation of interleukin-2 receptors

The capacity of retinoids to amplify the proliferative response of BALB/c lymphocytes to concanavalin A (Con A)² in the presence of exogenous interleukin-2 (IL-2) and the induction of IL-2 receptors (IL-2R) on L3T4⁺ and Lyt-2⁺ T-cells was evaluated. Preincubation with Con A for 8 h in the presence of retinoids resulted in a greater than two-fold increase in spleen cell proliferative response to Con A plus rIL-2 over the following 72 h relative to the response of cells preincubated with Con A alone. Peak potentiation of IL-2 responses occurred over a pharmacologic range of retinoic acid (RA) concentration (10⁻¹⁰−10⁻⁸ M) in the presence of 20 U/ml rIL-2. This potentiation of the response to IL-2 was likewise observed after 8 h prestimulation with Con A with splenic T-cells enriched by passage over nylon wool. Preincubation of the spleen cells with Con A plus RA without the subsequent addition of IL-2 resulted in a proliferative response that was potentiated nearly to the level of the response produced by subsequent addition of IL-2 to Con A-activated cells. Preincubation of the cells with Con A in the presence of RA produced a true synergy with IL-2; the resulting increase in response was greater than the sum of the increases produced by RA or IL-2 alone. By assessing the proportion of cells that became IL-2R positive during the early phase of cell activation by Con A and RA, it was determined that this augmentation by RA was apparently associated with increased IL-2R expression among L3T4⁺ (CD4), Lyt-2⁺ (CD8) and total T-cells. Indeed, RA-induced proliferative increases were significantly inhibited by addition to culture of anti-IL-2R antibodies. The potentiation of IL-2R expression by RA occurred early during Con A-activation suggesting that the kinetics of IL-2R expression were increased by RA. Indeed, near-maximal IL-2R expression was observed after a 12 h stimulation in the presence of RA, whereas maximal IL-2R expression in cultures containing only Con A occurred after 24 h. IL-2R expression was potentiated by RA in both CD4 and CD8 T-cells, but was potentiated more rapidly in the CD4 subpopulation. These data suggest that at least one of the mechanisms underlying retinoid potentiation of T-cell proliferation is the retinoid-induced increase in the rate of IL-2R expression.     

Analysis of thymic stromal cell subpopulations grown in vitro on extracellular matrix in defined medium. IV. Cytokines secreted by human thymic epithelial cells in culture and their activities on murine thymocytes and bone marrow cells.

In previous reports we described our approach to the cultivation of murine and human thymic epithelial cells in primary cultures, using defined, serum-free growth factor-supplemented medium and extracellular matrix-coated culture plates. The cells in these cultures displayed high metabolic activity and their supernatant was highly active on thymocytes. In the study reported here we analysed cytokine activities in the supernatant of human thymic epithelial cell cultures (HTES), by using the respective cytokine-dependent cell lines and by neutralization with specific monoclonal antibodies. Three cytokine activities were detected--interleukin-6 (IL-6), granulocyte colony-stimulating factor (G-CSF) and macrophage (M)-CSF. Other cytokine activities tested for [IL-1, IL-2, IL-7, interferon (IFN) and tumour necrosis factor (TNF)] were negative. The effect of HTES on concanavalin A (Con A)-induced proliferation of murine thymocytes could be completely abolished by anti-IL-6 antibodies, but not by antibodies to CSF, whereas enhancement of bone marrow cell proliferation by HTES was partially inhibited by either anti-G-CSF or anti-M-CSF antibodies and completely inhibited by both antibodies, but not at all by anti-IL-6. We can thus distinguish between thymocyte-related cytokines (IL-6) and bone marrow (myeloid/monocyte) related ones (G-CSF, M-CSF) in HTES.     

Immunomodulatory effects of neurotropin through the recovery of interleukin-2 production in autoimmune-prone (NZB/NZW) F1 mice

The immunomodulatory effects of Neurotropin, a substance extracted from inflammatory skin of rabbits inoculated with vaccinia virus, were assessed in autoimmune-prone (NZB/NZW) F1 (B/W F1) mice. The concanavalin A (Con A)-induced proliferative response of spleen cells was markedly decreased in aged B/W F1 mice as compared with young B/W F1 mice. Neurotropin, when administered i.p. to aged B/W F1 mice, significantly increased the Con A-induced proliferative response. In aged B/W F1 mice, interleukin-2 (IL-2) production by Con A-stimulated spleen cells was severely impaired and IL-2 responsiveness of Con A-activated spleen cells was partially decreased in comparison with young B/W F1 mice. Neurotropin, administered to the aged B/W F1 mice, restored IL-2 production by Con A-stimulated spleen cells to the level of young B/W F1 mice. Furthermore, Neurotropin completely restored the IL-2 responsiveness of Con A-activated spleen cells from aged B/W F1 mice. To test whether Neurotropin exerts its immunoregulatory activities in B/W F1 mice by restoring IL-2 production, we directly examined the effect of recombinant IL-2 on the immune functions of spleen cells in vitro. Recombinant IL-2 markedly enhanced Con A-induced proliferative response of aged B/W F1 mice. Furthermore, the suppressive activity of spleen cells which had been activated by Con A in the presence of rIL-2 was significantly increased. These results indicate that some immunoregulatory functions of aged B/W F1 mice can be corrected by IL-2 and suggest that Neurotropin restores immunoregulatory activity in B/W F1 mice by the recovery of IL-2 production.     

Lectin-induced cytotoxic activity in spleen cells from young and old mice. Age-related changes in types of effector cells, lymphokine production and response.

Concanavalin A (Con A)-induced cytotoxic activity, interferon (IFN) and interleukin-2 (IL-2) levels in cultures of spleen cells from young (2-3 months) and old (22-24 months) C57BL/6 female mice were studied. Con A-activated spleen cells from old mice attained significantly higher cytotoxic activity compared with activated spleen cells from young mice. Activated spleen cells from old and young mice showed differences in their ability to lyse different types of target cells. Both could lyse P-815 cells, neither could lyse K562 cells, and only activated cells from old mice could lyse EL-4 cells. Cytotoxic spleen cells from the old mice were more sensitive to anti-asialo-GM-1 and anti-Lyt-2.2 plus complement (C) treatment. While levels of IL-2 produced by spleen cells from young mice were higher, the addition of exogenous IL-2 had no effect on cytotoxic activity of the spleen cells from old mice. Exogenous IL-2, however, could lower cytotoxic activity of Con A-activated spleen cells from young mice. Activated spleen cells from old mice generated higher levels of IFN-gamma while the addition of an anti-IFN-gamma antibody boosted the level of cytotoxicity by Con A-activated spleen cells from young mice. These results suggest that IFN-gamma may act as a feedback inhibitory signal regulating the levels of cytotoxicity induced in spleen cells from young mice in response to Con A. The cytotoxic activity generated in Con A-activated spleen cells from old mice reflects a defect in this feed-back regulation.     

Concanavalin A-mediated polyclonal helper assay of normal thymocytes and its use for the analysis of ontogeny

A concanavalin A (Con A)-mediated polyclonal helper assay system was established by using the thymus cells or splenic T cells as a source of helper T cells. When splenic B cells were cocultured with thymus cells or splenic Lyt-2- T cells in the presence of an optimal dose of Con A, B Cells were polyclonally activated and differentiated into immunoglobulin-secreting cells. This Con A-mediated helper activity was completely inhibited by the addition of alpha-methyl-D-mannoside and could not be substituted by culture supernatant of Con A-stimulated thymocytes or splenic T cells. Almost all the activity of the thymus cells was carried by peanut agglutinin low binding population. Genetic restriction between T and B cells was not observed in this helper function. In ontogeny, Con A-mediated helper activity in the thymus was first detected at a few days after birth and reached the adult level at about 1 week of age. The polyclonal helper assay system developed in the present study provides a sensitive system to analyse the helper function of thymus cells and also to delineate the early phase of the differentiation of helper T cell population.     

Inhibition of T-lymphocyte activation by the immunosuppressive drug FK-506.

Nanamolar concentrations of the immunosuppressive drug FK-506 inhibit the induction of T-lymphocyte proliferation by the lectins concanavalin A (Con A) and phytohaemagglutinin (PHA). Activation by Con A is more sensitive to inhibition than the response to PHA. FK-506 inhibits an early Ca2+-dependent step in the activation process, and its effects are not reversible by the addition of recombinant interleukin-2 (IL-2) or lymphokine-rich culture supernatant. While the effects of suboptimal concentrations of FK-506 and cyclosporin A (CsA) are additive, FK-506 does not enhance the effects of optimal concentrations of CsA. Both drugs also have similar effects on the expression of specific mRNA in Con A-activated lymphocytes. A brief preincubation of unstimulated cells with FK-506 irreversibly inhibits their subsequent responsiveness to Con A. The mechanism of action of FK-506 thus resembles that of CsA, except that it is effective at two to three orders of magnitude lower concentrations and its effects are much less readily reversible.     

Human colostrum contains an activity that inhibits the production of IL-2.

The effect of human colostrum on T cell immune function was investigated. Colostrum inhibited the proliferation of human T cells activated by allogeneic, concanavalin A (Con A) or phytohaemagglutinin (PHA) stimulation. Colostrum also inhibited the production of IL-2 by Con A-activated human peripheral blood T cells and by Con A-activated Jurkat cells, a human T lymphoma line. Similarly, human colostrum inhibited the production of IL-2 by EL4 cells, a murine thymoma line, when stimulated with phorbol myristate acetate. The inhibitory activity was not cytotoxic and could not be neutralized by antibody to transforming human growth factor beta.     

Kinetic analysis of the immunopotentiating effect of the hypoxanthine analogue, NPT-15392, on the interleukin-2 production potential of human lymphocytes

Previous studies have shown that NPT-15392 (9-erythro-(2-hydroxy, 3-nonyl) hypoxanthine) enhances a variety of lymphoid functional activities including proliferative responses to various antigenic and mitogenic stimuli. In order to account at least partially for this immunopotentiation by NPT-15392, we examined the effects of this compound on interleukin-2 (IL-2) production by cultures of mitogen-activated human peripheral blood mononuclear cells (PBMC). Coculture of PBMC with NPT-15392 and concanavalin A (Con A) for 24 h resulted in significant increase of IL-2 in the supernatants of such cultures as compared with the IL-2 levels of control, non-NPT-treated, Con A-activated cultures. This enhancing effect was demonstrable with final culture concentrations of NPT-15392 ranging from 0.1 to 0.5 microgram/ml. Doses of NPT-15392 in excess of 5.0 micrograms/ml resulted in modest suppression of net IL-2 production. Pretreatment of PBMC with NPT-15392 for 2-4 h prior to activation with Con A was sufficient to achieve maximum enhancement of IL-2 production (20-40% average increase). Exposure of PBMC to NPT-15392 for longer periods (i.e. 24 h) did not result in higher levels of IL-2 production. NPT-15392 alone did not induce IL-2 synthesis at any of the doses employed and did not induce proliferation of the IL-2-dependent target cells used to quantitate IL-2 activity. Because of the multipotential role of IL-2 in the immune system, enhancement of IL-2 production by NPT-15392 may be a central pathway whereby this compound augments many lymphoid effector functions.     

Mouse B- and T-Cell Colony Formation in Vitro

Rat spleen cell cultures exposed for 24 h to concanavalin A (Con A-CM) contain, in addition to interleukin 2 (IL-2), factors that promote colony formation in vitro by mouse T cells (TCPA) and B cells (BCPA). TCPA and BCPA are separable on a Sephadex G-75 column. TCPA has a molecular weight of 15,000 daltons and shows the same elution profile as IL-2. Absorption studies with Con A-activated T cells suggested that TCPA and IL-2 are the same entity. BCPA has an apparent molecular weight of 45,000 daltons and stimulates colony formation by B lymphocytes seeded at very low cell density (10(4) - 5 X 10(4) cells/ml). In contrast to TCPA, BCPA can only be demonstrated in gel-filtered material owing to the presence of B colony suppressor activities in crude Con A-CM. Two B colony inhibitory activities were demonstrated by AcA 34 chromatography of crude Con A-CM with molecular weights of 80,000-130,000 and about 50,000, respectively. Because of the specificity, simplicity and sensitivity of B and T colony formation these assay systems should be valuable tools for in vitro testing of biological activities regulating the immune system.     

LFA-1/ICAM-1单抗对ConA诱导脾淋巴细胞增殖及分泌细胞因子的影响

通过研究ＬＦＡ－１／ＩＣＡＭ－１单抗对ＣｏｎＡ诱导的脾淋巴细胞活化增殖及其分泌细胞因子的影响　，探　讨了ＬＦＡ－１／ＩＣＡＭ－１分子在Ｔ细胞活化过程中所起的共刺激作用。结果表明，单独应用ＬＦＡ－１α链单抗（Ｍ１７／４．４．１１．９）或ＩＣＡＭ－１单抗（ＹＮ１／１．７．４）均不能引起脾淋巴细胞的增殖，但在加入ＣｏｎＡ诱导脾淋巴细胞增殖反应的最初８小时内加入ＬＦＡ－１单抗可以剂量依赖性地抑制ＣｏｎＡ诱导的脾淋巴细胞增殖反应及脾淋巴细胞分泌ＩＬ－２、ＩＰＮ－γ，而加入ＩＣＡＭ－１单抗却无此效应。说明ＬＰＡ－１在ＣｏｎＡ诱导的Ｔ细胞活化过程中起着重要的共刺激作用，ＬＰＡ－１通过与除ＩＣＡＭ－１以外的其它配体分子（如ＩＣＡＭ－３）相互识别，提供Ｔ细胞活化所必需的共刺激信号。     

Defect of suppressor cell induction in patients with juvenile rheumatoid arthritis

We studied the suppressor cell activity induced by concanavalin A (Con A) in 9 patients with acute febrile juvenile rheumatoid arthritis (JRA). The suppressor activity of JRA patients was higher than that of normal controls. However, the activity was significantly reduced by treating Con A-activated cells with mitomycin C (MMC) (P less than 0.05). On the other hand, the suppressor activity of normal controls and systemic lupus erythematosus (SLE) patients was not affected by MMC treatment. Two of 5 SLE patients showed low activity even before MMC treatment. The addition of the culture supernatant of Con A-stimulated peripheral blood mononuclear cells from a normal donor restored the induction of suppressor activity of JRA which was decreased by MMC treatment. The results indicated that patients with acute febrile type of JRA had reduced MMC resistant suppressor cell activity and that this was due to a defect in the ability of the cells to produce soluble factors needed to induce MMC resistant suppressor cells.     

Stimulation of splenic T-lymphocyte function by endogenous serotonin and by low-dose exogenous serotonin.

The modulatory effects of endogenous serotonin on splenic T-cell activity were investigated using two distinct approaches. The first approach showed that pretreatment of mice with p-cholorphenylalanine (PCPA) to deplete intracellular stores of serotonin reduced the capacity of their splenic T cells to proliferate and to express interleukin-2 receptor (IL-2R) in response to concanavalin A (Con A). These responses could be restored by the addition of serotonin to the spleen cell cultures. In contrast, PCPA treatment did not effect stimulation of spleen cells to produce IL-2. The second approach showed that T-cell proliferation to Con A as well as to IL-2 was diminished by the presence of antagonists to the serotonin-2 receptor (5-HT2R). The effects of low doses (100 ng/ml) of exogenously added serotonin on functions of normal spleen cells were also examined. At this low dose, serotonin stimulated splenic T-cell proliferation in response to IL-2, and enhanced both proliferation and IL-2 production in response to a suboptimal concentration of Con A. These results show autologous serotonin to be required for T-cell activation and that the activation of suboptimally stimulated T cells can be augmented with low doses of exogenously added serotonin. These data also suggest that the positive regulation of T-cell function by serotonin is mediated through 5-HT2R.     

Composite activities on B cells of products released by T cells activated by concanavalin A.

Supernatants from murine spleen cells cultured for 48 h in the presence of 1.0 μg of concanavalin A (Con A) induced polyclonal antibody synthesis in cultures of spleen cells from both normal and athymic mice in the absence of exogeneous antigen. Moreover, the Con A-induced supernatant rescued B cells which had been rendered unresponsive by a tolerogen [haptenated poly(D Glu,D Lys)]. The capacity of the supernatant to induce cell proliferation was studied under both high and low-density culture conditions. In contrast to antibody secretion, proliferation was only detectable in low-density cultures. The Con A-induced supernatant also contained suppressive components, since the primary anti-sheep red blood cell (SRBC) response was markedly suppressed when the antigen added to cultures consisted of SRBC which had previously been used for absorbing the supernatants. Absorbed supernatants displayed enhanced helper activity indicating that only the suppressor component was removable by antigen. The suppressive component was eluted from erythrocytes with ammonium thiocyanate and was itself strongly suppressive when added to cultures with fresh erythrocytes. Furthermore, the suppressive component proved to be highly antigen-specific, as the SRBC-absorbed factor did not affect the response to horse RBC. The results indicate that supernatants from Con A-activated spleen cells contain both helper and suppressor factors, the latter having easily demonstrable antigen specificity. They further suggest that a nonantigen-derived signal is sufficient to trigger both proliferation and antibody synthesis by B cells.     

Cytokine effects on a B-cell line

The murine pre-B-like cell line, 70Z /3, has been shown to undergo differentiation in response to supernatants derived from concanavalin-A (Con A) stimulated rat spleen cells or ultraviolet light treated P388D1 macrophage cell line. After culture for 24 h with supernatant factors, normally membrane IgM negative 70Z /3 cells are induced to synthesize light chain and become high level membrane IgM expressors . The cytokine (s) responsible for inducing 70Z /3 cells to differentiate is different from interleukin-2 (IL-2), B-cell growth factor (BCGF), colony-stimulating factor (CSF) I and II, but one of the cytokines is either very similar or identical to interleukin-1 (IL-1). These results demonstrate that IL-1 or a molecule with very similar physical properties can act directly on a B-cell line and thus probably also on normal B cells to influence differentiation.