Heavy and light chains of a mouse monoclonal autoantibody express the same idiotype

We report on the detection of the same idiotype (Id62) on the heavy and light chains of a mouse monoclonal autoantibody to thyroglobulin. This result was obtained by a simple, sensitive, and reproducible technique, namely immunoblot on nitrocellulose paper of electrophoretically separated heavy and light chains by using a panel of 125I-labeled anti-idiotype probes. These included polyclonal heterologous and syngeneic affinity-purified antibodies and a syngeneic monoclonal antibody. The immunoblot findings were confirmed through the solid-phase radioimmunoassay binding of the anti-idiotype probes to isolated H and L polypeptide chains prepared by conventional chromatography methods. Because anti-idiotype probes define a putative regulatory idiotype of the BALB/c autoimmune response to thyroglobulin, it is suggested that the simultaneous presence of the same idiotype on H and L chains may confer to antibody regulatory properties within the idiotypic network. The significance of the existence of the same idiotype on H and L chains and the implication of this finding for the regulation of the immune response to self antigens are discussed.

Heavy and light chains of a mouse monoclonal autoantibody express the same idiotype

We report on the detection of the same idiotype (Id62) on the heavy and light chains of a mouse monoclonal autoantibody to thyroglobulin. This result was obtained by a simple, sensitive, and reproducible technique, namely immunoblot on nitrocellulose paper of electrophoretically separated heavy and light chains by using a panel of 125I-labeled anti-idiotype probes. These included polyclonal heterologous and syngeneic affinity-purified antibodies and a syngeneic monoclonal antibody. The immunoblot findings were confirmed through the solid-phase radioimmunoassay binding of the anti-idiotype probes to isolated H and L polypeptide chains prepared by conventional chromatography methods. Because anti-idiotype probes define a putative regulatory idiotype of the BALB/c autoimmune response to thyroglobulin, it is suggested that the simultaneous presence of the same idiotype on H and L chains may confer to antibody regulatory properties within the idiotypic network. The significance of the existence of the same idiotype on H and L chains and the implication of this finding for the regulation of the immune response to self antigens are discussed.

B lymphocyte regulation of the immune system. II. Inhibition of Fc receptor expression of lymphocytes by BEF, a lymphokine of B cell origin

Recently, we described a new lymphokine of B cell origin, capable of selectively preventing the differentiation of T suppressor cells from the precursor into the effector stage. As a result, antibody production against various antigens is markedly increased. We termed this lymphokine B cell-derived enhancing factor (BEF). To discern the mechanism(s) by which BEF interferes with the activation of T suppressor cells, experiments were undertaken to explore the effect of BEF on the induction of Fc receptors (FcR). The induction of FcR on T cells has been implicated in the down-regulation of antibody synthesis, and it has been suggested that the expression of FcR for a given immunoglobulin precedes the release of factors with regulatory functions for the corresponding isotype. In the experiments reported here, murine spleen cells were incubated for 24 hr in the presence of IgG1 or IgA monoclonal antibodies, were washed, and the number of FcR gamma 1+ and FcR alpha+ cells were calculated by a rosette assay. The effect of BEF was studied either during the inductive phase or before, i.e., by pretreating the cells with BEF for 18 hr at 37 degrees C before the inductive phase. Our results show that BEF abolishes, in a dose-dependent manner, the expression of isotype-specific FcR in spleen cells when present during the inductive phase, as well as when cells are pretreated with it. In successive experiments, we tested the effect of BEF on the induction of FcR on T cell-enriched or B cell-enriched spleen cells. The results show that BEF is effective in selectively inhibiting FcR expression on T lymphocytes, but not on B lymphocytes, once isolated from the total spleen cell population. These findings provide further insight into the mechanism by which BEF modulates the immune response, and suggest that different mechanisms may be involved in the induction of FcR on T and B lymphocytes, respectively.

B lymphocyte regulation of the immune system. II. Inhibition of Fc receptor expression of lymphocytes by BEF, a lymphokine of B cell origin

Recently, we described a new lymphokine of B cell origin, capable of selectively preventing the differentiation of T suppressor cells from the precursor into the effector stage. As a result, antibody production against various antigens is markedly increased. We termed this lymphokine B cell-derived enhancing factor (BEF). To discern the mechanism(s) by which BEF interferes with the activation of T suppressor cells, experiments were undertaken to explore the effect of BEF on the induction of Fc receptors (FcR). The induction of FcR on T cells has been implicated in the down-regulation of antibody synthesis, and it has been suggested that the expression of FcR for a given immunoglobulin precedes the release of factors with regulatory functions for the corresponding isotype. In the experiments reported here, murine spleen cells were incubated for 24 hr in the presence of IgG1 or IgA monoclonal antibodies, were washed, and the number of FcR gamma 1+ and FcR alpha+ cells were calculated by a rosette assay. The effect of BEF was studied either during the inductive phase or before, i.e., by pretreating the cells with BEF for 18 hr at 37 degrees C before the inductive phase. Our results show that BEF abolishes, in a dose-dependent manner, the expression of isotype-specific FcR in spleen cells when present during the inductive phase, as well as when cells are pretreated with it. In successive experiments, we tested the effect of BEF on the induction of FcR on T cell-enriched or B cell-enriched spleen cells. The results show that BEF is effective in selectively inhibiting FcR expression on T lymphocytes, but not on B lymphocytes, once isolated from the total spleen cell population. These findings provide further insight into the mechanism by which BEF modulates the immune response, and suggest that different mechanisms may be involved in the induction of FcR on T and B lymphocytes, respectively.

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.

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.

The IgE antibody system is coordinately regulated by FcR epsilon-positive lymphoid cells and IgE-selective soluble factors

Recent studies in mice have demonstrated that exposure of lymphocytes to appropriate levels of IgE initiates a cascade of cellular and molecular interactions which function as a network to control IgE synthesis. A key manifestation of these events is the expression of Fc receptors for IgE (FcR epsilon) on both B and T lymphocytes, and the fact that such expression of FcR epsilon can be selectively modulated by the isotype-specific regulatory mediators, suppressive factor of allergy (SFA) and enhancing factor of allergy (EFA). In humans, we have previously shown that the in vitro induction by pokeweed mitogen (PWM) of IgE biosynthesis by peripheral blood lymphocytes (PBL) can also be selectively suppressed by SFA. Herein we show that PWM also induces expression of FcR epsilon+ and FcR gamma+ cells among human PBL by day 2 or 3 in culture, and this early development of FcR epsilon+ lymphocytes appears to be a coordinate event with the ultimate de novo synthesis of IgE in this system. Moreover, as previously documented for IgE synthesis, the presence of SFA causes a 50% reduction of FcR epsilon+ cells induced by PWM. This inhibition is selective, since FcR+ cells for IgG are not affected by exposure to human SFA derived from a recently constructed human T cell hybridoma line which constitutively secretes large quantities of biologically active human SFA. These findings further support the regulatory role that FcR epsilon+ lymphocytes must play in the development of IgE responses by human cells in vitro, and suggest a mechanism by which SFA can selectively inhibit IgE synthesis in PWM-stimulated cultures of human PBL.

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. III. Suppressive factor of allergy (SFA) is produced during the in vitro FcR epsilon expression cascade and displays corollary physiologic activity in vivo

Exposure of lymphoid cells to IgE induces the expression of Fc receptors for IgE (FcR epsilon) and the production of soluble mediators, termed IgE-induced regulants (EIR). Conventional suppressive factor of allergy (SFA) and enhancing factor of allergy (EFA), derived from mouse ascites fluids, both inhibit IgE-induced FcR epsilon expression in vitro in cultures of unfractionated and T cell-enriched, but not B cell-enriched, lymphoid cells. This indicates that the inhibitory activities of both entities are T cell dependent, and distinguishes them from the inhibitory EIRI, which inhibits FcR epsilon induction in the absence of T cells. Moreover, SFA and EFA can be distinguished from one another by differences in the T cell subsets required for the inhibitory activity of each respective mediator on in vitro IgE-induced FcR epsilon expression. Thus, SFA requires the presence of Lyt-1+ T cells, whereas EFA requires the presence of Lyt-2+ T cells. Supernatant fluids from IgE-stimulated unfractionated lymphoid cell cultures suppress in vivo IgE synthesis in mice, indicating that SFA is produced along with the other species of EIR. To define conditions required for SFA production in vitro, EIR-rich supernatant fluids were tested for the presence of SFA by using Lyt-2+ cell-blocked indicator cells in the in vitro FcR epsilon induction assay system (this eliminates the inhibitory activity of EFA). SFA production in vitro by IgE-stimulated lymphoid cells was shown to result from cooperative interactions between B cells and Lyt-1+ T cells. In addition, as observed with the induction of FcR epsilon in general, induction of SFA requires the initial interaction of B cells with IgE, and the release of the B cell-selective EIRB. Once produced, EIRB can directly stimulate Lyt-1+ cells, but not Lyt-2+ cells, to produce SFA. The physiologic significance of the in vitro induction of SFA by the action of EIRB on Lyt-1+ cells was confirmed by the demonstration that EIRB, devoid of detectable SFA, selectively suppressed in vivo IgE synthesis after administration to intact mice. This indicates that EIRB can stimulate resident T cells of irradiated SJL mice to produce SFA. Finally, as shown previously with conventional ascites-derived SFA, the SFA produced in vitro after stimulation of lymphoid cells with IgE is devoid of IgE-binding properties, because its inhibitory effects on in vivo IgE antibody synthesis are not removed by passage over IgE affinity columns.

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. I. A new class of molecules, termed IgE-induced regulants (EIR), which modulate FcR epsilon expression by lymphocytes

Exposure of unfractionated murine lymphoid cells to suitable amounts of IgE in vitro results in the de novo expression of Fc receptors for IgE (FcR epsilon) by both T and B lymphocytes. Monoclonal IgE, in the monomeric state, directly induces FcR epsilon expression by B cell-enriched but not T cell-enriched lymphoid cells. In contrast, the same monoclonal IgE in the aggregated state can directly induce FcR epsilon expression by either lymphocyte class independently. The fact that monomeric IgE induces almost equal proportions of FcR epsilon+ B and T cells unfractionated cell cultures, but can directly induce only FcR epsilon+ B cells when lymphocyte subpopulations are independently exposed to IgE, suggested the involvement of either soluble mediators or cognate interactions in this FcR epsilon expression process. Indeed, the studies presented demonstrate that IgE-stimulated lymphoid cells produce soluble mediators, termed IgE-induced regulants (EIR), which can induce FcR epsilon expression in cultures of fresh lymphoid cells. EIR-stimulated FcR epsilon expression is independent of IgE in either its native or processed state, and is largely by T cells of the Lyt-2+ subset. Thus, total depletion of T cells or more selective elimination of the Lyt-2+ subset prevented the development of FcR epsilon+ cells in cultures exposed to EIR but not in those exposed to monomeric IgE. Conversely, depletion of B cells had the opposite effect in that the remaining T cells retained the ability to express FcR epsilon in response to EIR but were unresponsive to monomeric IgE. Because of its selective activity in inducing FcR epsilon expression by T lymphocytes, EIR from unfractionated lymphoid cell cultures has been designated EIRT. This selectivity of EIRT inductive properties for T lymphocytes was additionally confirmed by analyses of the FcR epsilon+ lymphoid cells subsequent to induction with IgE or EIRT. Thus, unlike monomeric IgE, which induces FcR epsilon+ cells equally distributed among T and B lymphocytes, EIRT induces FcR epsilon+ cells in only the T cell class. These findings indicate that production of the EIRT and subsequent expression of FcR epsilon by Lyt-2+ T cells depends upon the initial interaction of IgE with B cells. Finally, an interesting paradox observed was that although IgE-induced FcR epsilon expression by B cells is unaffected by total T cell depletion, selective blocking of just Lyt-1+ T cells significantly diminishes this FcR epsilon induction process.(ABSTRACT TRUNCATED AT 400 WORDS)

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. I. A new class of molecules, termed IgE-induced regulants (EIR), which modulate FcR epsilon expression by lymphocytes

Exposure of unfractionated murine lymphoid cells to suitable amounts of IgE in vitro results in the de novo expression of Fc receptors for IgE (FcR epsilon) by both T and B lymphocytes. Monoclonal IgE, in the monomeric state, directly induces FcR epsilon expression by B cell-enriched but not T cell-enriched lymphoid cells. In contrast, the same monoclonal IgE in the aggregated state can directly induce FcR epsilon expression by either lymphocyte class independently. The fact that monomeric IgE induces almost equal proportions of FcR epsilon+ B and T cells unfractionated cell cultures, but can directly induce only FcR epsilon+ B cells when lymphocyte subpopulations are independently exposed to IgE, suggested the involvement of either soluble mediators or cognate interactions in this FcR epsilon expression process. Indeed, the studies presented demonstrate that IgE-stimulated lymphoid cells produce soluble mediators, termed IgE-induced regulants (EIR), which can induce FcR epsilon expression in cultures of fresh lymphoid cells. EIR-stimulated FcR epsilon expression is independent of IgE in either its native or processed state, and is largely by T cells of the Lyt-2+ subset. Thus, total depletion of T cells or more selective elimination of the Lyt-2+ subset prevented the development of FcR epsilon+ cells in cultures exposed to EIR but not in those exposed to monomeric IgE. Conversely, depletion of B cells had the opposite effect in that the remaining T cells retained the ability to express FcR epsilon in response to EIR but were unresponsive to monomeric IgE. Because of its selective activity in inducing FcR epsilon expression by T lymphocytes, EIR from unfractionated lymphoid cell cultures has been designated EIRT. This selectivity of EIRT inductive properties for T lymphocytes was additionally confirmed by analyses of the FcR epsilon+ lymphoid cells subsequent to induction with IgE or EIRT. Thus, unlike monomeric IgE, which induces FcR epsilon+ cells equally distributed among T and B lymphocytes, EIRT induces FcR epsilon+ cells in only the T cell class. These findings indicate that production of the EIRT and subsequent expression of FcR epsilon by Lyt-2+ T cells depends upon the initial interaction of IgE with B cells. Finally, an interesting paradox observed was that although IgE-induced FcR epsilon expression by B cells is unaffected by total T cell depletion, selective blocking of just Lyt-1+ T cells significantly diminishes this FcR epsilon induction process.(ABSTRACT TRUNCATED AT 400 WORDS)

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. II. FcR epsilon+ B lymphocytes initiate a cascade of cellular and molecular interactions that control FcR epsilon expression and IgE production

This study additionally explores the orderly sequence of events concerning the induction of Fc receptors for IgE (FcR epsilon) that are initiated by IgE and mediated by IgE-induced regulants (EIR). Thus, lymphoid cells exposed to monomeric IgE displayed an early phase of exclusive B cell FcR epsilon expression, followed by the progressive appearance of FcR epsilon+ T cells, ultimately resulting in equal proportions of FcR epsilon+ B cells and T cells. Parallel cultures of lymphoid cells stimulated with EIR derived from unfractionated lymphoid cells (EIRT) also manifested rapid induction of FcR epsilon+ cells, but these FcR epsilon+ cells were predominantly T cells from the outset. Data presented here demonstrate that IgE-induced FcR epsilon expression by B cells ultimately results in the production of EIRT, which then induces FcR epsilon expression by T cells. The existence of EIRT that selectively induce T cell FcR epsilon expression prompted us to search for an EIRB that is selectively active in inducing FcR epsilon+ B cells. Indeed, IgE-stimulated, T cell-depleted lymphoid cells produce an EIRB that selectively induces FcR epsilon expression by B cells. This EIRB, but not EIRT, can also be generated by IgE stimulation of Lyt-2+ cell-blocked lymphoid cells, indicating that Lyt-1+ cells are not inhibitory to EIRB production and that production of EIRT is dependent upon functionally competent Lyt-2+ cells. Similar to IgE, EIRB induces rapid FcR epsilon expression, first by B cells and then by T cells, so that by 16 hr post induction equal proportions of FcR epsilon+ B and T cells were observed. Although complete T cell depletion does not affect IgE-induced FcR epsilon expression, selective blocking of Lyt-1+ cells markedly diminishes such responses, suggesting that Lyt-2+ cells are antagonistic to the induction of FcR epsilon+ B cells. Studies involving sequential T cell subset depletion clearly demonstrated that in the absence of functionally competent Lyt-1+ cells, Lyt-2+ cells exert an inhibitory influence on IgE-induced FcR epsilon expression by B cells. Stimulation of Lyt-1+ cell-blocked cultures with EIRT, and to a lesser degree with IgE, resulted in the elaboration of an EIR (EIRI), which lacks direct FcR epsilon-inductive properties, but conversely, directly inhibits IgE-induced FcR epsilon expression in fresh B cell cultures.

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. II. FcR epsilon+ B lymphocytes initiate a cascade of cellular and molecular interactions that control FcR epsilon expression and IgE production

This study additionally explores the orderly sequence of events concerning the induction of Fc receptors for IgE (FcR epsilon) that are initiated by IgE and mediated by IgE-induced regulants (EIR). Thus, lymphoid cells exposed to monomeric IgE displayed an early phase of exclusive B cell FcR epsilon expression, followed by the progressive appearance of FcR epsilon+ T cells, ultimately resulting in equal proportions of FcR epsilon+ B cells and T cells. Parallel cultures of lymphoid cells stimulated with EIR derived from unfractionated lymphoid cells (EIRT) also manifested rapid induction of FcR epsilon+ cells, but these FcR epsilon+ cells were predominantly T cells from the outset. Data presented here demonstrate that IgE-induced FcR epsilon expression by B cells ultimately results in the production of EIRT, which then induces FcR epsilon expression by T cells. The existence of EIRT that selectively induce T cell FcR epsilon expression prompted us to search for an EIRB that is selectively active in inducing FcR epsilon+ B cells. Indeed, IgE-stimulated, T cell-depleted lymphoid cells produce an EIRB that selectively induces FcR epsilon expression by B cells. This EIRB, but not EIRT, can also be generated by IgE stimulation of Lyt-2+ cell-blocked lymphoid cells, indicating that Lyt-1+ cells are not inhibitory to EIRB production and that production of EIRT is dependent upon functionally competent Lyt-2+ cells. Similar to IgE, EIRB induces rapid FcR epsilon expression, first by B cells and then by T cells, so that by 16 hr post induction equal proportions of FcR epsilon+ B and T cells were observed. Although complete T cell depletion does not affect IgE-induced FcR epsilon expression, selective blocking of Lyt-1+ cells markedly diminishes such responses, suggesting that Lyt-2+ cells are antagonistic to the induction of FcR epsilon+ B cells. Studies involving sequential T cell subset depletion clearly demonstrated that in the absence of functionally competent Lyt-1+ cells, Lyt-2+ cells exert an inhibitory influence on IgE-induced FcR epsilon expression by B cells. Stimulation of Lyt-1+ cell-blocked cultures with EIRT, and to a lesser degree with IgE, resulted in the elaboration of an EIR (EIRI), which lacks direct FcR epsilon-inductive properties, but conversely, directly inhibits IgE-induced FcR epsilon expression in fresh B cell cultures.

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. IV. Delineation of target cells and mechanisms of action of SFA and EFA in inhibiting in vitro induction of FcR epsilon expression

SFA and EFA are derived from distinct mouse T cell hybridomas secreting one or the other (but not both) factor, and although both are capable of inhibiting FcR epsilon expression by unfractionated spleen cells induced by monomeric IgE, neither was inhibitory for EIRT-induced FcR epsilon expression by T cells in the same cell population. This suggests that the final target cell for the inhibitory effects of SFA and EFA is the FcR epsilon+ B lymphocyte. T cells are required for both SFA- and EFA-mediated FcR epsilon inhibition, and more precisely, as shown in this study, SFA stimulates Lyt-1+ cells in the presence or absence of IgE to produce a suppressive effector molecule (SEM), and EFA together with IgE stimulates Lyt-2+ cells to produce an enhancing effector molecule (EEM), both of which can directly inhibit FcR epsilon expression by B cells. SFA and SEM can inhibit both IgE- and EIRB-induced FcR epsilon expression by B cells, indicating that SFA may act by blocking the EIRB-mediated expansion of the FcR epsilon+ B cell population. EFA and EEM, in contrast, can inhibit IgE-induced but not EIRB-induced FcR epsilon expression, indicating that EFA may act at some point before the release of EIR, perhaps involving those FcR epsilon+ B cells that respond to IgE and produce EIRB. Finally, although neither SFA and EFA display IgE binding properties, both SEM and EEM, in contrast, are IgE binding factors (IgE-BF) and may be homologous to the suppressive IgE binding factor and potentiating IgE binding factor described by other investigators. The possible interrelationships between these various cells and factors are discussed.

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. III. Suppressive factor of allergy (SFA) is produced during the in vitro FcR epsilon expression cascade and displays corollary physiologic activity in vivo

Exposure of lymphoid cells to IgE induces the expression of Fc receptors for IgE (FcR epsilon) and the production of soluble mediators, termed IgE-induced regulants (EIR). Conventional suppressive factor of allergy (SFA) and enhancing factor of allergy (EFA), derived from mouse ascites fluids, both inhibit IgE-induced FcR epsilon expression in vitro in cultures of unfractionated and T cell-enriched, but not B cell-enriched, lymphoid cells. This indicates that the inhibitory activities of both entities are T cell dependent, and distinguishes them from the inhibitory EIRI, which inhibits FcR epsilon induction in the absence of T cells. Moreover, SFA and EFA can be distinguished from one another by differences in the T cell subsets required for the inhibitory activity of each respective mediator on in vitro IgE-induced FcR epsilon expression. Thus, SFA requires the presence of Lyt-1+ T cells, whereas EFA requires the presence of Lyt-2+ T cells. Supernatant fluids from IgE-stimulated unfractionated lymphoid cell cultures suppress in vivo IgE synthesis in mice, indicating that SFA is produced along with the other species of EIR. To define conditions required for SFA production in vitro, EIR-rich supernatant fluids were tested for the presence of SFA by using Lyt-2+ cell-blocked indicator cells in the in vitro FcR epsilon induction assay system (this eliminates the inhibitory activity of EFA). SFA production in vitro by IgE-stimulated lymphoid cells was shown to result from cooperative interactions between B cells and Lyt-1+ T cells. In addition, as observed with the induction of FcR epsilon in general, induction of SFA requires the initial interaction of B cells with IgE, and the release of the B cell-selective EIRB. Once produced, EIRB can directly stimulate Lyt-1+ cells, but not Lyt-2+ cells, to produce SFA. The physiologic significance of the in vitro induction of SFA by the action of EIRB on Lyt-1+ cells was confirmed by the demonstration that EIRB, devoid of detectable SFA, selectively suppressed in vivo IgE synthesis after administration to intact mice. This indicates that EIRB can stimulate resident T cells of irradiated SJL mice to produce SFA. Finally, as shown previously with conventional ascites-derived SFA, the SFA produced in vitro after stimulation of lymphoid cells with IgE is devoid of IgE-binding properties, because its inhibitory effects on in vivo IgE antibody synthesis are not removed by passage over IgE affinity columns.

FcR epsilon+ lymphocytes and regulation of the IgE antibody system. IV. Delineation of target cells and mechanisms of action of SFA and EFA in inhibiting in vitro induction of FcR epsilon expression

SFA and EFA are derived from distinct mouse T cell hybridomas secreting one or the other (but not both) factor, and although both are capable of inhibiting FcR epsilon expression by unfractionated spleen cells induced by monomeric IgE, neither was inhibitory for EIRT-induced FcR epsilon expression by T cells in the same cell population. This suggests that the final target cell for the inhibitory effects of SFA and EFA is the FcR epsilon+ B lymphocyte. T cells are required for both SFA- and EFA-mediated FcR epsilon inhibition, and more precisely, as shown in this study, SFA stimulates Lyt-1+ cells in the presence or absence of IgE to produce a suppressive effector molecule (SEM), and EFA together with IgE stimulates Lyt-2+ cells to produce an enhancing effector molecule (EEM), both of which can directly inhibit FcR epsilon expression by B cells. SFA and SEM can inhibit both IgE- and EIRB-induced FcR epsilon expression by B cells, indicating that SFA may act by blocking the EIRB-mediated expansion of the FcR epsilon+ B cell population. EFA and EEM, in contrast, can inhibit IgE-induced but not EIRB-induced FcR epsilon expression, indicating that EFA may act at some point before the release of EIR, perhaps involving those FcR epsilon+ B cells that respond to IgE and produce EIRB. Finally, although neither SFA and EFA display IgE binding properties, both SEM and EEM, in contrast, are IgE binding factors (IgE-BF) and may be homologous to the suppressive IgE binding factor and potentiating IgE binding factor described by other investigators. The possible interrelationships between these various cells and factors are discussed.

Human IgE synthesis in vitro by pokeweed mitogen-stimulated human lymphoid cells: verification with a reconfirmed epsilon-specific radioimmunoassay

This study was performed to address the controversy concerning human IgE biosynthesis in vitro induced by stimulation with pokeweed mitogen (PWM) or other agents. The controversy has focused on the specificity of reagents employed for quantitatively determining human IgE in culture supernatant fluids. Specifically, questions have been raised as to whether certain anti-human IgE antibody reagents possess anti-idiotypic reactivities, thereby resulting in reactions with Fab determinants of polyclonal immunoglobulins which would yield false-positive readings of IgE protein levels. We present a detailed analysis confirming that the goat anti-human IgE antibody designated GAHE(PS), which was initially isolated by affinity chromatography with the same IgE(PS) myeloma protein used for immunization, binds poorly, if at all, with IgG, IgA, or IgM immunoglobulins, even at excessive concentrations (100 micrograms/ml). Moreover, GAHE(PS) displayed no reactivity with Fab fragments of IgG or free L-chains prepared from pooled polyclonal IgG isolated from Cohn fraction II. A second GAHE reagent was prepared by purification by affinity chromatography on a second, completely unrelated IgE myeloma protein (DZA), which differed from IgE(PS) in light chain class, thereby resulting in a reagent, designated GAHE(DZA), which was completely devoid of any possible reactivity with L-chain or idiotypic determinants affiliated with IgE(PS). By utilizing both reagents, the studies presented here confirmed that PWM-stimulated human lymphoid cell cultures synthesize increased quantities of IgE, which can be detected in comparable amounts by both GAHE(DZA) and GAHE(PS) in supernatant fluids from such cultures. Because incorporation of the reversible protein synthesis inhibitor, cycloheximide, totally abolished the PWM-induced increases in IgE levels in such cultures, these results verify that such increases reflect de novo synthesis of human IgE as a result of PWM stimulation in vitro.

IgE class-restricted tolerance induced by neonatal administration of soluble or cell-bound IgE. Cellular mechanisms

Certain aspects of the phenomenon of IgE class-restricted tolerance induced in mice by neonatal treatment with monoclonal IgE, either in soluble form or coupled to syngeneic spleen cells, were examined. The present studies document that this tolerance results from exposure to IgE molecules, irrespective of their antigen specificity, and the resulting effects are polyclonal in nature since IgE responses directed against antigenic determinants unrelated to the tolerance-inducing IgE molecules are affected. Moreover, such findings indicate that the molecular subregion(s) responsible for inducing IgE class-restricted tolerance resides in the epsilon heavy chain constant region domain(s) of IgE. When soluble IgE is employed, tolerance induction results from neonatal treatment with doses as low as 2.5 micrograms per injection per mouse; cell-bound IgE is considerably more potent, in terms of total dose required, since tolerance results from treatment with as few as 1 X 10(6) cells per injection (per mouse), equivalent to an absolute quantity of 0.2 ng of IgE per injection. This long-term class-specific tolerance appears to be a unique feature of the IgE antibody system, since treatment of mice with monoclonal antibodies of the IgA, IgG1, or IgG2b isotypes, either in soluble or cell-bound form, does not perturb antibody responses of their corresponding isotypes or in the IgE class. By analyzing the lymphoid cells of IgE-tolerant mice after they reached adulthood, the following observations were made: (a) lymphoid cells from such tolerant mice fail to develop FcR epsilon + cells upon in vitro stimulation with IgE, as is characteristically observed with lymphoid cells from nontolerant mice; and (b) mice rendered tolerant by neonatal treatment with soluble IgE possess IgE class-restricted suppressor T cells, demonstrable in adoptive transfer experiments, whereas no such suppressor cells are evident in mice in which cell-bound IgE was used for neonatal treatment. The latter observations could mean that two different mechanisms underlie the IgE class-restricted tolerance, or both mechanisms operate coordinately to varying degrees depending upon which regimen is used for tolerance induction, as discussed herein.

Human IgE synthesis in vitro by pokeweed mitogen-stimulated human lymphoid cells: verification with a reconfirmed epsilon-specific radioimmunoassay

This study was performed to address the controversy concerning human IgE biosynthesis in vitro induced by stimulation with pokeweed mitogen (PWM) or other agents. The controversy has focused on the specificity of reagents employed for quantitatively determining human IgE in culture supernatant fluids. Specifically, questions have been raised as to whether certain anti-human IgE antibody reagents possess anti-idiotypic reactivities, thereby resulting in reactions with Fab determinants of polyclonal immunoglobulins which would yield false-positive readings of IgE protein levels. We present a detailed analysis confirming that the goat anti-human IgE antibody designated GAHE(PS), which was initially isolated by affinity chromatography with the same IgE(PS) myeloma protein used for immunization, binds poorly, if at all, with IgG, IgA, or IgM immunoglobulins, even at excessive concentrations (100 micrograms/ml). Moreover, GAHE(PS) displayed no reactivity with Fab fragments of IgG or free L-chains prepared from pooled polyclonal IgG isolated from Cohn fraction II. A second GAHE reagent was prepared by purification by affinity chromatography on a second, completely unrelated IgE myeloma protein (DZA), which differed from IgE(PS) in light chain class, thereby resulting in a reagent, designated GAHE(DZA), which was completely devoid of any possible reactivity with L-chain or idiotypic determinants affiliated with IgE(PS). By utilizing both reagents, the studies presented here confirmed that PWM-stimulated human lymphoid cell cultures synthesize increased quantities of IgE, which can be detected in comparable amounts by both GAHE(DZA) and GAHE(PS) in supernatant fluids from such cultures. Because incorporation of the reversible protein synthesis inhibitor, cycloheximide, totally abolished the PWM-induced increases in IgE levels in such cultures, these results verify that such increases reflect de novo synthesis of human IgE as a result of PWM stimulation in vitro.

Induction of autoantibodies to thyroglobulin by anti-idiotypic antibodies

We report on the induction of autoantibodies to thyroglobulin (Tg) and idiotype-positive molecules (Id') in naive BALB/c mice and Buffalo (BUF) rats after immunization with affinity-purified rabbit anti-Id antibodies directed against the Id of a mouse monoclonal antibody ( mAb62 ) specific for a hormone-containing epitope of Tg. Autoantibodies to Tg were produced in about one-half of anti-Id immunized mice, whereas Id' was detected in all but one mouse. Autoantibodies to Tg and Id' were not produced in control mice similarly immunized with non-anti-Id Ig. To clarify the relationship between molecules with Tg-binding activity and those referred to as Id', Tg-specific monoclonal antibodies were generated from an anti-Id-immunized mouse. By competitive inhibition experiments, we could determine that they were idiotypically very similar to the monoclonal antibody ( mAb62 ) at the origin of the immunologic cascade. Thus, autoantibodies induced by anti-idiotypic immunization alone are likely to be of the Ab1' type. Similarly, autoantibody to Tg and Id' molecules were induced in young normal rats of the autoimmune-prone BUF strain. Together, these results suggest that antibodies to Id directed against autoantigens are sufficient per se to activate self-reactivity.

Induction of autoantibodies to thyroglobulin by anti-idiotypic antibodies

We report on the induction of autoantibodies to thyroglobulin (Tg) and idiotype-positive molecules (Id') in naive BALB/c mice and Buffalo (BUF) rats after immunization with affinity-purified rabbit anti-Id antibodies directed against the Id of a mouse monoclonal antibody ( mAb62 ) specific for a hormone-containing epitope of Tg. Autoantibodies to Tg were produced in about one-half of anti-Id immunized mice, whereas Id' was detected in all but one mouse. Autoantibodies to Tg and Id' were not produced in control mice similarly immunized with non-anti-Id Ig. To clarify the relationship between molecules with Tg-binding activity and those referred to as Id', Tg-specific monoclonal antibodies were generated from an anti-Id-immunized mouse. By competitive inhibition experiments, we could determine that they were idiotypically very similar to the monoclonal antibody ( mAb62 ) at the origin of the immunologic cascade. Thus, autoantibodies induced by anti-idiotypic immunization alone are likely to be of the Ab1' type. Similarly, autoantibody to Tg and Id' molecules were induced in young normal rats of the autoimmune-prone BUF strain. Together, these results suggest that antibodies to Id directed against autoantigens are sufficient per se to activate self-reactivity.

Spontaneous proliferation in unfractionated spleen cell cultures: autologous mixed-lymphocyte reactions (AMLR) which can be differentially regulated by prostaglandins and lymphokines

The present studies were undertaken to define the contribution of the autologous or syngeneic mixed-leukocyte reactions (AMLR/SMLR) to the cellular proliferation observed in unfractionated spleen cell cultures. Proliferation was studied in whole, untreated 6-day murine spleen cell cultures supplemented with syngeneic serum. These cultures exhibited relatively low but significant levels of cellular proliferation as measured by uptake of radioactive thymidine ([3H]TdR). Treatment of spleen cells with monoclonal anti-Thy 1.2 antibody and complement before culture, the addition of specific anti-I-A monoclonal antibodies to the cultures or removal of Ia+ adherent cells before initiation of culture all inhibited the proliferative response significantly. Thus, the autologous proliferation of untreated and unfractionated spleen cells manifests the main characteristics of the AMLR/SMLR, namely, its dependence on T (responder) and Ia+ (stimulator) cells and specific inhibition by anti-I-A antibodies. A marked augmentation in cellular proliferation was observed in unfractionated spleen cell cultures treated for the initial 24 hr of culture with 5 X 10(-6) M indomethacin, an inhibitor of prostaglandin synthesis. Conversely, the addition of 7 X 10(-9) M prostaglandin E1 (PGE1) to these cultures depressed cellular proliferation. This suppression of autologous splenic cell proliferation induced by PGE1 could be partially reversed by the addition of concanavalin A-induced lymphokine (LK) preparations early in the culture. These findings indicate that (a) the proliferation of unfractionated spleen cell cultures occurring in the absence of exogenous stimulatory signals is due largely to an ongoing AMLR, and (b) biologically active mediators with opposing influences, namely, prostaglandins and immunostimulatory LK, participate in the regulation of the AMLR.