B lymphocyte regulation of the immune system. I. In vivo biologic activity of the novel lymphokine, B cell-derived enhancing factor (BEF)

B cell-derived enhancing factor (BEF) is a lymphokine of B cell origin which was originally identified and characterized by its ability to enhance in vitro antibody responses, an effect shown to be due to the ability of BEF to reduce the activation of suppressor T cells. The present study was undertaken to determine whether BEF could also be active in modulating antibody responses in vivo. The data presented here demonstrate that BEF is biologically active in vivo, as manifested by significantly enhanced primary IgM and IgG antibody responses in mice that were either injected with BEF prepared exogenously or implanted with growing BEF-secreting cells of a B cell line. Moreover, BEF was shown to enhance subsequent development of immunologic memory in mice pretreated with BEF at the time of primary immunization; these mice then displayed enhanced secondary responses when challenged with the same antigen some weeks later. The mechanism by which BEF exerts biologic activities to positively modulate in vivo antibody responses and immunologic memory reflects the ability of BEF to modulate one or more T cell functions, as evidenced by the following findings. 1) Transient in vitro exposure to BEF of T cells, but not of B cells, endowed such cells with the capacity to adoptively transfer enhanced primary antibody responses to irradiated recipients. 2) Utilizing adoptive in vivo antibody responses, in which fractionated B cell or T cell populations were obtained from BEF-pretreated mice, revealed that one effect of BEF which results in enhanced immunologic memory is related to its activity on T cells during the priming phase of the immune response. Finally, the existence of this B cell-derived lymphokine and the demonstration of its in vivo regulatory effects on the immune system provide yet another example of the emerging biologic importance of B lymphocytes in the overall regulation of the immune system.     

Comparison of the action of carminomycin and rubomycin on the dynamics of the primary and secondary immune responses

The effect of rubomycin and carminomycin on the dynamics of the primary and secondary immune response and formation of the immunologic memory to sheep red cells in mice was studied. Differences in the character of the antibiotics effect indicative of the higher selective action of carminomycin on multiplying cells, precursors of the antibody-forming plasmids, were found. Theoretically interesting discrepancies in the effect of the antibiotics on the content of the antibodies in the serum and the antibody-producing cells in the spleen were shown. It was demonstrated that carminomycin had no effect on formation of the immunologic memory inspite of a noticeable decrease in the total number of the spleen nuclear cells and the number of the antibody-forming cells at the moment of immunization under the effect of the antibiotic.     

The effect of the antigen-induced splenic suppressor factor on the immune response to different antigens

Quick-frozen spleen of mice immunized with sheep red blood cells was homogenized and centrifuged. Supernatant was used as a source of suppressor factor (SF). It was shown that SF inhibited antibody immune response to thymus-dependent antigens and delayed hypersensitivity reaction. SF did not inhibit antibody formation to thymus-independent antigen. SF activity disappeared after its treatment with anti-Ig immunosorbent.     

A quantitative model suggests immune memory involves the colocalization of B and Th cells.

A prominent and essential feature of the humoral immune response of vertebrates is immunologic memory: the ability to recall previous exposure to antigen. We present a mathematical model of the growth and interactions of the major cell populations involved in the humoral immune response. Our analysis of this model predicts that the formation of a dynamic association between small numbers of antigen-specific B and Th cells, "colocalization", is sufficient to account for memory and the kinetics of the secondary response--neither specifically differentiated Th or B memory cells nor networks of antigen and anti-idiotypes are required. The colocalization hypothesis explains a number of existing experimental observations and can be tested by straightforward experiments which we describe.     

Study of the phenomenon of specific suppression of the immune response in an adoptive transfer system]

It was revealed that the administration of the spleen cells (SC) of syngeneic animals immunized with a high dose of sheep red blood cells (SRBC) to intact mice led to a marked specific suppression of the recipients' immune response. The donors' SC obtained on the 14th day after the intraperitoneal injection of SRBC had the greatest suppressive activity. The SC of intact animals and mice given rat erythrocytes preliminarily failed to influence the immune response of the intact recipients in their SRBC immunization. Treatment of immune SC with the anti-T-serum (ATS) or the anti-B-globulin (ABG) and the complement considerably decreased or completely eliminated the suppressive activity. Administration of a mixture of two immune SC suspensions one of which was ATS- and another ABC-treated did not produce any suppression of the immune response in the intact recipients. It is supposed that the suppressor cells in the given model were T-lymphocytes expressing the antigens, common of cross-reacting with the B-cells.     

Resistance of the suppressor function of T-cells to agents possessing an antiproliferative action]

Administration of cyclophosphamide in a dose of 50 to 400 mg/kg to mice immunized with sheep red blood cells failed to decrease significantly the capacity of the splenic cells of these mice to suppress the primary immune response in transplantation to intact syngeneic recipients. Irradiation of the donors of immune splenic cells (ISC) in a dose of 900 r or treatment of ISC in vitro with mitomycin C failed to influence their suppressor activity. Supernatant obtained after the ultracentrifugation of ISC treated with ultrasound inhibited the primary immune response of intact mice. A conclusion was drawn that the suppressor effect of ISC was caused by the factor produced by T-cells. Active proliferation of these cells was not necessary for the realization of its action.     

Immunosuppression during viral oncogenesis. IV. Generation of soluble virus-induced immunologic suppressor molecules

We describe herein functional attributes and generation of immunologic suppressor activity elaborated in response to oncogenic virus infection. Malignant rabbit fibroma virus-induced immunologic suppressor factor (VISF) is a T cell product produced in peak quantities by spleen cells taken from infected rabbits 7 days after infection in vivo. Its production does not appear to require macrophage participation. VISF is highly labile, 3.5 to 12 kDa, and capable of suppressing both B and T lymphocytic responses. Indomethacin and the cyclic nucleotides cAMP and cGMP inhibit its generation. VISF activity is neither antigen nor species specific. It suppresses murine and leporine immune responses to antigens unrelated to the inducing virus. Comparable suppressor activity may be induced by infecting an apparently non-functional rabbit T lymphoma line, RL-5, with malignant rabbit fibroma virus. VISF is principally a suppressor-inducer factor: in vitro, lymphocytes exposed to VISF do not show decreased immunologic responsiveness until 4 days of culture. VISF induces T suppressor cell activity when normal spleen cells are exposed briefly to VISF. Thus, immunosuppressive consequences of malignant fibroma virus infection are partially mediated by a small, non-specific T cell-derived suppressor lymphokine with unique functional characteristics. Non-specific immunologic dysfunction that often attends virus infections may reflect the activity of such factors in humans as well.     

Activity of concanavalin A-induced suppressor cells in human MLR: differential effects on primary MLR, secondary MLR, and memory cell precursors

The relative sensitivity of the MLR responses of freshly isolated human lymphocytes to Con A-induced suppressor cells (SC) was compared to that of lymphocytes that had been primed previously in vitro. Fresh and primed cells were suppressed 72 and 17%, respectively, when cultured under similar conditions (p less than 0.0005). Titration of SC indicated that equivalent suppression in the two populations would require greater than a 50-fold excess of SC in the primed cells. Neither preincubation of the primed cells for 24 or 72 hr with the SC before restimulation, addition of fresh autologous cells to the primed cells, nor preincubation of the SC with fresh cells before addition to the primed cells increased suppression of primed cells. SC added at the beginning of a primary MLC were, however, very suppressive for both the primary response (67% suppression) and the subsequent secondary response (81% suppression). These data indicate that although the human primary MLR and the precursor of the memory cell are both sensitive to the suppressors induced by Con A, the memory cell itself possess an intrinsic resistance to such suppressors that is not related to simple kinetic phenomena nor to the loss in vitro of an intermediate regulatory cell. Cell depletion experiments suggest that resistance to nonspecific suppression may occur at the level of the helper cell.     

The nature of the suppressive effect of interferon and interferon inducers on the in vitro immune response

Viral-induced interferon inhibition of the primary in vitro plaque-formong cell (PFC) response in the mouse (C57B1/6) involves a dynamic relationship between the nature of the antigen, the concentration of interferon added to antigen-stimulated cultures, and the time of addition of interferon relative to antigen addition. The PFC response to a thymus-dependent antigen (sheep red blood cells) was more easily suppressed by viral-induced interferon than was that to a thymus-independent antigen (E. coli 0127 LPS), both in terms of inhibitory concentrations of interferon and the time at which the interferon could be added to cultures after antigen and still inhibit the PFC response. These differential effects of interferon could be related to the difference in cellular requirements (B and T lymphocytes) of the two antigens. Interferon was effective in inhibiting the in vitro PFC response of antigen-primed spleen cells, indicating that it can block the response of memory lymphocytes. By using interferon inducers as inhibitors of the in vitro PFC response, it was possible to show that at least two antigenically distinct interferons may be involved in suppressing the immune response. It is known that one type of interferon is induced by virus and synthetic double-stranded polyribonucleotides. The other type is stimulated by antigen and T cell mitogens. A model is proposed to explain the nature of these interferon inhibitory effects in terms of mediation of immune suppressor cell effects.     

Enhancement of in vivo immune response by tumor necrosis factor

Interleukin 1 (IL-1) has been shown to regulate several immunologic functions. Since tumor necrosis factor (TNF) shares many biologic properties with IL-1, we have investigated here the role of TNF in the modulation of the immune response. We have thus tested low doses of human recombinant TNF-alpha (hu rTNF-alpha) for its capacity to enhance the in vivo antibody responses evaluated at the cellular level in the hemolytic plaque assay. It was found that hu rTNF-alpha, like human IL-1 beta, is able to enhance the immune response to a T cell-dependent antigen (sheep red blood cells). Interestingly, at variance with human recombinant IL-1 beta, hu rTNF-alpha was not able to enhance the in vivo antibody response to a T cell-independent antigen (type III pneumococcal polysaccharide). These results suggest that low levels of TNF may have a role in the modulation of the immune response in vivo and shed new light on the biologic significance of this mediator.     

Cells participating in immunologic memory induced with RNA from the spleens of immunized mice

Ribonucleic acid (immune RNA, iRNA) extracted from the spleens of mice immunized with heterologous red blood cells induced antigen-specific immunologic memory. The type of cells (T cells, B cells) which participate in immunologic memory induced with iRNA was investigated. Immune RNA-primed T cells cooperated with normal, iRNA-primed or antigen-primed B cells and induced a high IgM response. Immune RNA-primed B cells did not cooperate with normal T cells, but did with iRNA- or antigen-primed T cells. The activities of iRNA-primed T and B cells were antigen-specific.     

A role for antigen in the maintenance of immunological memory

The immune system has a memory that it exhibits in the enhanced and augmented responses the second time it meets an antigen. The memory is the result of a number of changes to the system brought about during the primary response. The most important of these changes is the formation of an expanded pool of antigen-specific memory cells. One of the enduring questions in immunology is how these memory cells are maintained for such long periods.     

Effect of trypsin on suppressor cell formation and function in localized staphylococcal infection

The present study has been made on (CBA X C57BL)F1 mice immunized with sheep red blood cells (SRBC) and inoculated with staphylococci (M-SRBC-S). The injection of splenic lymphocytes from syngeneic M-SRBC-S into intact mice has been found to suppress immune response to SRBC in these mice. The injection of trypsin into M-SRBC-S decreases the suppressive action of their lymphocytes on SRBC-induced immune response in syngeneic recipients. The injection of trypsin into the recipients has been found to produce no effect on the immunosuppressive action of transplanted lymphocytes obtained from M-SRBC-S. The injection of trypsin into M-SRBC-S induces the release of the factor, inhibiting the formation and function of suppressor cells, by their splenocytes. Previously formed suppressor cells block the release of the immunostimulating factor by the splenocytes of the animals receiving the injections of trypsin.     

Alterations in the Immunogenic Properties of Sheep Erythrocytes by Sonic Disruption

A solubilized sheep red blood cell (SRBC) antigen (supernatant fraction obtained by centrifuging 10^7-2 × 10⁸ sonicated SRBC at 6 × 10⁴ g for 30 min [Sup-SRBC]), whose ability to inhibit anti-SRBC plaque formation was 70% of that of the original sonicated SRBC, was unable to elicit a detectable antibody response in either unprimed or SRBC-primed mice. However, Sup-SRBC as well as intact SRBC antigens generated memory for the secondary response, which was transferable to irradiated syngeneic recipients by injection of immune spleen cells. The memory generated by Sup-SRBC involved helper memory for anti-trinitrophenyl group (TNP) response to challenge with TNP-conjugated SRBC. Increase in the helper T cell memory in the spleens of Sup-SRBC-primed mice was also demonstrated by an in vitro culture experiment and by an adoptive cell transfer experiment. In contrast, no detectable B cell memory was generated by Sup-SRBC. Repeated stimulation with Sup-SRBC never induced significant antibody response but reduced the level of memory. A single injection of a low dose (10⁶) of SRBC also failed to induce a definite primary antibody response generating memory for the secondary response. However, repeated stimulation with this dose of SRBC induced a high antibody response and generated good memory. From these results it is suggested that the intact structure of SRBC is required for the activation of B cells, but is not necessary for the stimulation of T cells.     

The role of complement receptor positive and complement receptor negative B cells in the primary and secondary immune response to thymus independent type 2 and thymus dependent antigens

Both complement receptor positive (CR+) and complement receptor negative (CR-) B cells have been shown to be involved in the primary immune response to PC-Hy (phosphocholine conjugated hemocyanin), a thymus dependent (TD) antigen which preferentially induces antibody secretion in Lyb-5+ B cells during a primary adoptive transfer assay. CR+ and CR- B cells also responded in a primary adoptive transfer assay to TNP-Ficoll, a thymus independent type 2 (TI-2) antigen which activates only Lyb-5+ B cells. When the secondary immune response to PC-Hy and TNP-Ficoll were analyzed, it was found that most of the immune memory to both antigens was present in the CR- B cell subset. The CR- B cell subset also dominated the secondary immune response to PC-Hy in immune defective (CBA/N X DBA/2N)F1 male mice. These data indicate that CR- B cells dominate the memory response in both the Lyb-5+ and Lyb-5- B cell subsets of normal and xid immune defective mice and suggest that Lyb-5+ and Lyb-5- B cells can be subdivided into CR+ and CR- subsets.     

Short-term stress experienced at time of immunization induces a long-lasting increase in immunologic memory

It would be extremely beneficial if one could harness natural, endogenous, health-promoting defense mechanisms to fight disease and restore health. The psychophysiological stress response is the most underappreciated of nature's survival mechanisms. We show that acute stress experienced before primary immunization induces a long-lasting increase in immunity. Compared with controls, mice restrained for 2.5 h before primary immunization with keyhole limpet hemocyanin (KLH) show a significantly enhanced immune response when reexposed to KLH 9 mo later. This immunoenhancement is mediated by an increase in numbers of memory and effector helper T cells in sentinel lymph nodes at the time of primary immunization. Further analyses show that the early stress-induced increase in T cell memory may stimulate the robust increase in infiltrating lymphocyte and macrophage numbers observed months later at a novel site of antigen reexposure. Enhanced leukocyte infiltration may be driven by increased levels of the type 1 cytokines, IL-2 and IFN-gamma, and TNF-alpha, observed at the site of antigen reexposure in animals that had been stressed at the time of primary immunization. In contrast, no differences were observed in type 2 cytokines, IL-4 or IL-5. Given the importance of inducing long-lasting increases in immunologic memory during vaccination, we suggest that the neuroendocrine stress response is nature's adjuvant that could be psychologically and/or pharmacologically manipulated to safely increase vaccine efficacy. These studies introduce the novel concept that a psychophysiological stress response is nature's fundamental survival mechanism that could be therapeutically harnessed to augment immune function during vaccination, wound healing, or infection.     

Enhancement of reaginic and hemagglutinating antibody production by an extract of Bordetella pertussis containing histamine sensitizing factor.

The effect of an extract containing the histamine-sensitizing factor (HSF) of Bordetella pertussis on the immune response of mice to ovalbumin was investigated with respect to dose of antigen and adjuvant. Of particular interest was the enhancement of reaginic antibody production. In comparison to the Al(OH)3 induced production of reaginic antibody where low doses of antigen and adjuvant yield high titers of reagin, the HSF extract demonstrated optimal adjuvant activity at high doses of both adjuvant and antigen. The reaginic antibody response was maximal usually by 2 to 3 weeks post-immunization and persisted for long periods of time. The hemagglutinating antibody response was maximal at 8 to 10 weeks post-immunization. The initial treatment of mice with HSF extract plus antigen resulted in the production of memory cells since a subsequent immunization with ovalbumin alone evoked a secondary reaginic response. These observations may have implications in clinical allergy since substances similar to the pertussis factor might be produced by other microbial organisms and these substances could modulate the immunologic response of individuals to common allergens.     

T cell subset interactions in the regulation of syngeneic tumor immunity

Suppressor T cell (Ts) regulation of immunity to chemically induced syngeneic tumors has been investigated with regard to the mechanism of Ts stimulation and cell-to-cell communication. It has been determined that suppressor cells generated by the presence of tumor antigen participate in a suppressive circuit involving both cells and cell-derived factor(s) in the expression of suppressive effects. Evidence is provided that these interactions occur via idiotype--antiidiotype recognition in a manner similar to those in hapten-specific immune response. Conditions for induction of Ts activity in vivo have been artificially created by a variety of means, including the intravenous administration of soluble antigen and the inhibition of antigen-presenting function by anti-I-A antibodies or by in vivo treatment with ultraviolet irradiation. Suppression appears to be directed against the Ly-1+ cell, which mediates tumor immunity in this system. The summary of evidence suggest that responses to tumor antigen are in many aspects analogous to those occurring in response to more conventional antigens, but are subject to the dampening effects of suppressor cells generated continually during the period of primary tumor growth.     

Cell-mediated amplification and down regulation of cytotoxic immune response against autologous human cancer

The cytotoxic host immune response toward autologous human cancer may be regulated by the immunoregulatory network. Here we show that helper T cells, cloned from peripheral blood lymphocytes that were sensitized in vitro against an autologous human malignant paraganglioma, proliferated against and made interleukin 2 when cocultured with the tumor-associated antigen in the presence of autologous accessory cells. Furthermore, the helper cell clones amplified cytotoxic immune response by peripheral blood lymphocytes against the paraganglioma cells in coculture with the blood lymphocytes and the paraganglioma cells. An autologous T cell line bearing suppressor phenotype, established from a lymph node that had been infiltrated with the paraganglioma tumor cells, in contrast to the helper cells, selectively suppressed the cytotoxic immune response by the blood lymphocytes against the paraganglioma cells in identical coculture. These results, therefore, demonstrate the existence of cell-mediated immunologic regulations of the cytotoxic immune response (concurrent amplification and suppression in the same host) against an autologous human tumor.     

The extracorporeal immunostimulating effect of terrilytin in staphylococcal infection]

The intravenous injection of terrilytin-treated lymphocytes into rats infected with staphylococci enhances the formation of staphylococcal alpha antitoxin in the animals and the development of immune response to T-dependent antigen, such as sheep red blood cells (SRBC), but produces no effect on the development of immune response induced by T-independent antigen (lipopolysaccharide). Terrilytin-treated lymphocytes induce the release of the factor promoting the development of immune response to staphylococcal antigens and SRBC by spleen cells, incapable of adherence to plastic, but have no influence on the development of immune response to lipopolysaccharide in rats infected with staphylococci. At the same time in such rats spleen cells adhering to plastic take part in the transfer of signals from terrilytin-treated lymphocytes to nonadhering spleen cells of recipients.