Human IgE antibody synthesis in vitro: stimulation of IgE responses by pokeweed mitogen and selective inhibition of such responses by human suppressive factor of allergy (SFA)

The studies presented herein provide details of an in vitro system in which IgE biosynthesis by human peripheral mononuclear cells can be stimulated by exposure to pokeweed mitogen (PWM). Mononuclear cells of normal donors or patients with hyperimmunoglobulinemia E were cultured in 2 stages, the first stage consisting of exposure of cells to stimulating mitogen; after this first stage incubation, cells were washed and replated in cultures devoid of any additional mitogen for a further 6 days. Under such conditions, human mononuclear cells were shown to synthesize significant quantities of IgE. Both T cells and surface IgE-bearing cells were shown to be necessary in order to obtain an IgE response in this system. Supernatants from 2-way human mixed lymphocyte cultures were shown to contain an IgE class-specific suppressive factor capable of selectively inhibiting in vitro IgE (and not IgG) biosynthesis. This model can be used to compare the regulation of IgE synthesis in normal and atopic donors, and further experiments examining the production and action of this class-specific suppressive factor may have prognostic and therapeutic implications.

Analysis of T cell function in autoimmune murine strains. Defects in production and responsiveness to interleukin 2

In the studies reported here, we have analyzed the production and consumption of T cell growth factor, more recently termed interleukin 2 (IL-2), as well as some cell-mediated immune functions, in murine strains [MRL, BXSB, NZB, and (NZB x NZWF1] manifesting systemic lupus erythematosus (SLE)-like syndromes. Young (4-6 wk) or old (4-8 mo) autoimmune or normal mice were studied and compared with regard to the following T cell functions in vitro after stimulation with concanavalin A (Con A): (a) mitogenic response; (b) IL-2 levels in culture supernates; and (c) the ability to respond to and adsorb IL-2. In addition, proliferative activity in the allogeneic mixed leukocyte culture and frequency of alloreactive cytotoxic T lymphocyte precursors (CTLp) were analyzed in some of these strains. Reduced Con A-induced mitogenic responses and IL-2 production appeared at 3-6 wk of age in the early, severe SLE developing strains MRL-Mp-lpr/lpr (MRL/l) and male BXSB and progressed thereafter. Similar defects appeared at a later stage in MRL/Mp-+/+ and (NZB x NZW)F1 hybrid mice, which develop late disease. Detailed analysis of cells from the enlarged lymph nodes and spleens of older MRL/l mice demonstrated that such cells: (a) responded poorly to Con A or allogeneic stimulator cells, even in the presence of exogenous IL-2; (b) did not suppress IL-2 production by normal spleen cells; (c) were relatively incapable of adsorbing or inactivating IL-2; and (d) had a markedly reduced anti-H-2b CTLp frequency in the mesenteric lymph nodes but a normal one in spleen. These results indicate that the proliferating Thy-1.2+, Lyt-1+ T cells in MRL/l mice are defective in their responses to mitogenic stimuli, in IL-2 production, and in expression of acceptor sites for IL-2. The relevance of these defects to the MRL/l disease as well as to the role of IL-2 in autoimmunity in general remains to be determined.

Human IgE antibody synthesis in vitro: stimulation of IgE responses by pokeweed mitogen and selective inhibition of such responses by human suppressive factor of allergy (SFA)

The studies presented herein provide details of an in vitro system in which IgE biosynthesis by human peripheral mononuclear cells can be stimulated by exposure to pokeweed mitogen (PWM). Mononuclear cells of normal donors or patients with hyperimmunoglobulinemia E were cultured in 2 stages, the first stage consisting of exposure of cells to stimulating mitogen; after this first stage incubation, cells were washed and replated in cultures devoid of any additional mitogen for a further 6 days. Under such conditions, human mononuclear cells were shown to synthesize significant quantities of IgE. Both T cells and surface IgE-bearing cells were shown to be necessary in order to obtain an IgE response in this system. Supernatants from 2-way human mixed lymphocyte cultures were shown to contain an IgE class-specific suppressive factor capable of selectively inhibiting in vitro IgE (and not IgG) biosynthesis. This model can be used to compare the regulation of IgE synthesis in normal and atopic donors, and further experiments examining the production and action of this class-specific suppressive factor may have prognostic and therapeutic implications.

Stimulation of primary in vitro IgE antibody responses in culture of human peripheral mononuclear cells

Experiments are presented herein that demonstrate the capacity to stimulate human peripheral mononuclear cells to synthesize and secrete significant quantities of IgE molecules in vitro by exposure to appropriate concentrations of 2,4-dinitrophenyl (DNP)-protein conjugates, pokeweed mitogen (PWM), or a combination of DNP-proteins and PWM. Cultures stimulated in this fashion synthesize increased quantities of both total IgE and DNP-specific IgE antibody molecules. This in vitro human IgE antibody system should provide a useful tool for further exploration of regulatory control of IgE responses in both normal humans and those manifesting various forms of IgE-mediated allergic disorders.

Immature B cells as the target for in vivo tolerance induction

In vitro studies have indicated that immature B cells at a specific stage in clonal maturation are exquisitely susceptible to tolerance induction by antigens and antigen concentrations that have no effect on mature B cells. In order to determine if a similar phenomenon obtains for B cells in vivo, mice were tolerized with DNP-D-GL and their splenic and bone marrow B cells were carefully washed and analyzed for responsiveness in the splenic focus system. The results demonstrate that, whereas the treated mice themselves become rapidly unresponsive to either DNP or TNP on a heterologous carrier, a measurable decrease in the frequency of splenic DNP-responsive B cells occurs only very slowly with a half-life of approximately 2 wk and TNP-responsive splenic B cells are only marginally, if at all, affected. A progressive decrease in DNP-responsive bone marrow B cells is also observed and occurs at a somewhat more rapid rate than the decrease in splenic B cells. The rate of decrease of splenic precursor cells is totally consistent with the normal attrition of mature B cells in the absence of newly generated DNP-specific B cells. Thus, in vivo tolerance, like in vitro tolerance may only eliminate immature B cells as they emerge from their stem cell pool and has no effect on mature resident B cells. This conclusion is consistent with the additional finding that 1 mo after tolerance induction, the majority of remaining DNP-responsive B cells in the bone marrow is found in very early precursors that have not, as yet, acquired their immunoglobulin receptors. Finally, the exquisite specificity of this tolerance induction would be totally consistent with a physiologic role for a clonal abortion mechanism that could specifically eliminate self-reactive B cells while leaving essentially intact the B cell repertoire responsive to non-self determinants.

Immature B cells as the target for in vivo tolerance induction

In vitro studies have indicated that immature B cells at a specific stage in clonal maturation are exquisitely susceptible to tolerance induction by antigens and antigen concentrations that have no effect on mature B cells. In order to determine if a similar phenomenon obtains for B cells in vivo, mice were tolerized with DNP-D-GL and their splenic and bone marrow B cells were carefully washed and analyzed for responsiveness in the splenic focus system. The results demonstrate that, whereas the treated mice themselves become rapidly unresponsive to either DNP or TNP on a heterologous carrier, a measurable decrease in the frequency of splenic DNP-responsive B cells occurs only very slowly with a half-life of approximately 2 wk and TNP-responsive splenic B cells are only marginally, if at all, affected. A progressive decrease in DNP-responsive bone marrow B cells is also observed and occurs at a somewhat more rapid rate than the decrease in splenic B cells. The rate of decrease of splenic precursor cells is totally consistent with the normal attrition of mature B cells in the absence of newly generated DNP-specific B cells. Thus, in vivo tolerance, like in vitro tolerance may only eliminate immature B cells as they emerge from their stem cell pool and has no effect on mature resident B cells. This conclusion is consistent with the additional finding that 1 mo after tolerance induction, the majority of remaining DNP-responsive B cells in the bone marrow is found in very early precursors that have not, as yet, acquired their immunoglobulin receptors. Finally, the exquisite specificity of this tolerance induction would be totally consistent with a physiologic role for a clonal abortion mechanism that could specifically eliminate self-reactive B cells while leaving essentially intact the B cell repertoire responsive to non-self determinants.

A clonal analysis of the IgE response and its implications with regard to isotope commitment

In a clonal analysis of the IgE response, it was found that a small proportion of primary or nonimmune B cells in spleen and mesenteric lymph nodes can be stimulated by antigen to produce IgE-secreting clones. In addition, there appears to be no substantial difference in the frequency of such cells between the classical low and high IgE responder strains. An analysis of immune, or memory, B cells revealed substantial increases in the frequency of B cells secreting IgE as compared with primary B cells, although the actual proportion of B cells secreting IgE remained relatively low. When the IgE-secreting clones derived from either primary or secondary B cells were reanalyzed for the presence of other isotypes, it was found that all clones secreting IgE were secreting at least one other isotype, with the majority secreting two or three other isotypes in addition to IgE. This demonstrates that there is no distinct subpopulation of B cells committed to IgE expression per se.

Cell-interaction molecules on immunocompetent lymphocytes. Development of anti-parent cell-interaction-molecule-receptor reactions in F1 hybrid mice and evidence for a unique F1 hybrid subset of interacting cells

The experiments presented herein demonstrate that F1-parent T-B cell cooperation in vivo is significantly diminished by the addition of lymphoid cells of opposite parental type. This inhibition phenomenon is not a straightforward allosuppression mechanism as (a) it can be induced by parental lymphoid cells depleted by T cells, (b) it does not operate on cooperative interactions between homologous T and B cells of opposite parental type, and (c) absolutely requires the presence of F1 cells as participants in the reactions generated. The possible involvement of alloantibodies produced aberrantly under the experimental conditions employed has been ruled out by direct macrophage/antigen-presenting cell components of the reactions has been excluded. Because the presence of parental lymphoid cells only affects cooperative interactions between F1 T cells and B lymphocytes of opposite parental type but has no inhibitory effect on cooperative interactions between homologous F1, T and B cells, this (and other points discussed herein) strongly argues for the existence of one or more subsets of F1 interacting partner cells that are uniquely specific for F1, as distinct from either parental type cell interaction determinants. For reasons discussed, it appears that the most likely mechanism underlying such parental cell-induced inhibitory effects on F1-parent partner cell interactions is the development of anti-self cell interaction structure responses by F1 cells against the relevant self-specific cell-interaction structures of the parental partner cells involved.

Differentiation of murine bone marrow stem cells in vitro: long-term growth promoted by a lymphocyte-derived mediator

In attempts to induce differentiation of lymphoid cells from hematopoietic stem cells in vitro, the effects of allogeneic effect factor on the growth of murine bone marrow cultures were studied. Allogeneic effect factor is a soluble mediator derived from mixed secondary murine leukocyte cultures. For several weeks it supported the growth of bone marrow cultures, as indicated by the maintenance of stem cell activity, cellular proliferation, and heterogeneity. Another lymphokine, T cell growth factor, did not, Pre-T lymphocytes could be detected in these cultures for several weeks.

"Allergic breakthrough" after antigen sensitization: height of IgE synthesis is temporally related to diurnal variation in endogenous steroid production

Mice of the SJL strain normally display the low IgE responder phenotype. In the course of extensive studies on IgE responses with this strain of mice, it because apparent that the magnitudes of IgE antibody synthesis by SJL mice varied after antigen sensitization either alone or in conjunction with exposure to optimal enhancing doses of whole body irradiation. Analysis of the basis for this variability revealed that SJL respond to antigen sensitization by displaying cyclical IgE response curves determined by the time of day the sensitization is carried out. Moreover, when these low responders are converted to the high responder phenotype by low dose irradiation, the time of irradiation determines the magnitude of the IgE response obtained, whereas the time of antigen challenge determines the potential for generating a good response. The diurnal curve of IgE responses in both unirradiated and irradiation-enhanced low responder mice appears to be determined by normal variations in levels of endogenous corticosteroids, as indicated by the correlation between the normal diurnal curve of endogenous steroid production with the cyclical pattern of IgE responses. This apparent effect of endogenous steroid production on IgE antibody synthesis is supported by experiments demonstrating that the normal IgE pattern in both unirradiated and irradiated mice can be perturbed by administration of cortisone at the proper time of day. These results indicate that IgE antibody synthesis displays unique sensitivity to fluctuations in plasma steroid levels and may have significant implications for the role of steroids in the pathogenesis and management of allergic diseases.

"Allergic breakthrough" after antigen sensitization: height of IgE synthesis is temporally related to diurnal variation in endogenous steroid production

Mice of the SJL strain normally display the low IgE responder phenotype. In the course of extensive studies on IgE responses with this strain of mice, it because apparent that the magnitudes of IgE antibody synthesis by SJL mice varied after antigen sensitization either alone or in conjunction with exposure to optimal enhancing doses of whole body irradiation. Analysis of the basis for this variability revealed that SJL respond to antigen sensitization by displaying cyclical IgE response curves determined by the time of day the sensitization is carried out. Moreover, when these low responders are converted to the high responder phenotype by low dose irradiation, the time of irradiation determines the magnitude of the IgE response obtained, whereas the time of antigen challenge determines the potential for generating a good response. The diurnal curve of IgE responses in both unirradiated and irradiation-enhanced low responder mice appears to be determined by normal variations in levels of endogenous corticosteroids, as indicated by the correlation between the normal diurnal curve of endogenous steroid production with the cyclical pattern of IgE responses. This apparent effect of endogenous steroid production on IgE antibody synthesis is supported by experiments demonstrating that the normal IgE pattern in both unirradiated and irradiated mice can be perturbed by administration of cortisone at the proper time of day. These results indicate that IgE antibody synthesis displays unique sensitivity to fluctuations in plasma steroid levels and may have significant implications for the role of steroids in the pathogenesis and management of allergic diseases.

Construction of T cell hybridomas secreting allogeneic effect factor

T cell hybridoma lines were constructed by fusion of DBA/2 alloantigen-activated T cell blasts with the AKR thymoma line BW5147. Certain of the hybridomas prepared in this manner secreted spontaneously into their culture supernates biologically active molecules that displayed B cell- and T cell-activating properties characteristic of allogeneic effect factor (AEF). Cell surface phenotype analysis documented that the hybridomas were, indeed, somatic cell hybrids between the two respective partner cells used for fusion. The B cell-activating properties of these hybridoma supernates was demonstrated by their capacity to stimulate T cell-depleted spleen cells to respond in vitro to T-dependent antigens. The T cell-activating properties of these hybridoma supernates was verified by their capacity to stimulate autonomous development of self-specific cytotoxic T lymphocytes and by their capacity to exert mitogenic effects on unprimed T cells. The biologically active molecules secreted by these hybridomas were, like conventional AEF, inhibitable by specific anti-Ia antibodies thus indicating the presence of Ia determinants on the relevant hybridoma products. Finally, these AEF-secreting hybridomas could be stimulated to proliferate and to secrete increased quantities of AEF when exposed to the specific alloantigen-bearing target cells to which the T cell blasts had been originally sensitized.

Existence of T cells manifesting self-reactivity indistinguishable from alloreactivity

The studies reported here were designed to analyze the phenotypic characteristics of self-reactive T lymphocytes induced in culture by allogeneic effect factor (AEF), as well as the control of their functional activities by the major histocompatibility complex (MHC). Unprimed T cells cultured with AEF in the absence of exogenous stimulating target cells become activated against self-antigens, as evidenced by their ability to manifest two distinct activities. First, such cells could lyse syngeneic target cells. This cytolytic activity was directed against H-2K antigens and was mediated by Lyt-2+ T cells. Second, the AEF-activated T cells could be stimulated in a secondary culture to high levels of proliferative activity by irradiated syngeneic spleen cells. The stimulator cells in this syngeneic mixed lymphocyte reaction (MLR) were found to be Thy-1-negative, Ia-positive splenic adherent cells. Stimulation in the secondary syngeneic MLR was provided by I-region specificities, and the majority of the proliferating cells were Lyt-1+ cells. Finally, AEF-induced T cells were effective in serving as effectors of graft-vs-host reactions in vivo in syngeneic recipients. These results prove that, under appropriate conditions, murine T lymphocytes can display aggressive patterns of self-reactivity that are similar in both quantity and quality to the classical patterns of alloreactivity and may have great significance for our understanding of MHC recognition processes.

Existence of T cells manifesting self-reactivity indistinguishable from alloreactivity

The studies reported here were designed to analyze the phenotypic characteristics of self-reactive T lymphocytes induced in culture by allogeneic effect factor (AEF), as well as the control of their functional activities by the major histocompatibility complex (MHC). Unprimed T cells cultured with AEF in the absence of exogenous stimulating target cells become activated against self-antigens, as evidenced by their ability to manifest two distinct activities. First, such cells could lyse syngeneic target cells. This cytolytic activity was directed against H-2K antigens and was mediated by Lyt-2+ T cells. Second, the AEF-activated T cells could be stimulated in a secondary culture to high levels of proliferative activity by irradiated syngeneic spleen cells. The stimulator cells in this syngeneic mixed lymphocyte reaction (MLR) were found to be Thy-1-negative, Ia-positive splenic adherent cells. Stimulation in the secondary syngeneic MLR was provided by I-region specificities, and the majority of the proliferating cells were Lyt-1+ cells. Finally, AEF-induced T cells were effective in serving as effectors of graft-vs-host reactions in vivo in syngeneic recipients. These results prove that, under appropriate conditions, murine T lymphocytes can display aggressive patterns of self-reactivity that are similar in both quantity and quality to the classical patterns of alloreactivity and may have great significance for our understanding of MHC recognition processes.

Induction of immunologic tolerance to the trimellitate haptenic group in mice: model for a therapeutic approach to trimellitic anhydride-induced hypersensitivity syndromes in humans?

IgE and IgG antibody responses to the trimellitate (TM) hapten group were elicited in mice by the intraperitoneal injection of the hapten coupled with keyhole limpet hemocyanin (KLH). Treatment of such previously sensitized mice with the same hapten coupled to synthetic copolymer of D-glutamic acid and D-lysine (D-GL) after primary immunization resulted in significant and specific suppression of anti-TM antibody responses in both IgE and IgG classes. These results provide direct evidence for the potential clinical usefulness of the D-GL immunotherapeutic approach to TMA sensitivity in humans.