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E Kölsch

Publications and source records attributed to E Kölsch.

At least 19 recordsLinked to original sources
PubMed2001

Prostaglandins, but not tumor-derived IL-10, shut down concomitant tumor-specific CTL responses during murine plasmacytoma progression.

IL-10 is assumed to be a major immunosuppressive factor produced by most B-cell tumors. The immunosuppressive role of tumor-derived IL-10 was analyzed using the MHC class II-negative BALB/c plasmacytoma ADJ-PC-5 as a model tumor. Immune monitoring of tumor-bearing mice was based on the measurement of tumor burden, tumor-specific CTL cytotoxicity and intracellular cytokine staining using FACS. ADJ-PC-5 tumor progression in syngeneic recipients is associated with strong, concomitant, tumor-specific CTL responses during early stages of tumor progression which are sufficient to cause rejection of small s.c. autologous test tumors. These initial CTL responses gradually decline during later tumor stages. Blocking of IL-10 in vivo did not abolish CTL suppression or retard tumor growth. More strikingly, application of anti-IL-10 antibodies during early tumor stages abrogated CTL induction and markedly accelerated tumor growth. In contrast to anti-IL-10 treatment, application of cyclo-oxygenase inhibitors to ADJ-PC-5 tumor-bearing mice led to enhanced tumor-specific CTL responses throughout all stages of tumor progression, paralleled by retarded tumor growth and a significantly delayed onset of suppression. Both findings contradict a dominant immunosuppressive role of IL-10 during B-cell tumor progression. Tumor-derived IL-10 must therefore be considered an immunostimulating factor, which accounts for the high immunogenicity of B-cell tumors, whereas prostaglandins, which are not produced by the tumor cells themselves, are the dominant immunosuppressors in this system.

Animals↗
PubMed2001

T-cell enforced invariance of the antibody repertoire in the immune response against a bacterial carbohydrate antigen.

The humoral response against the bacterial polysaccharide antigen alpha(1-->3) dextran (Dex) is controlled by J558 idiotype-(Id) specific T cells. These T cells of which the cell clone 178-4 Ts is a representative by all relevant criteria, recognize J558 Id-bearing B cells in an I-Ed-restricted manner. Costimulation via CD28/B7-1 but not via CD40/CD40L leads to T-cell activation. These T cells do not only suppress B cells producing the immunoglobulin (Ig)G3 isotype but also support the survival and clonal expansion of J558 Id positive B cells both in vivo and in vitro. This T-cell mediated dominance of the J558 idiotype limits the appearance of antibodies carrying other more diverse idiotypes which appear in immunized BALB/c nu/nu mice where no regulatory T cells occur. This T-cell mediated antibody invariance could be a strategy of the immune system responding to highly conserved antigens like polysaccharides, different from those against protein antigens, where diversity is assumed to be the basis for a successful response.

Animals↗
PubMed2001

T cell mediated antibody invariance in an immune response against a bacterial carbohydrate antigen requires CD28/B7-1 costimulation.

The humoral immune response against alpha(1-->3) dextran (Dex) in BALB/c mice is characterized by the formation of predominantly IgM antibodies bearing the J558 idiotype. IgG antibodies do not appear in euthymic mice. In athymic animals however, the response proceeds to a vigorous IgG production. In euthymic mice formation of IgG is suppressed by J558 idiotype-specific regulatory T cells recognizing in association with I-Ed and in cognate T/B interaction the VH CDR3 derived peptide of the J558 idiotpye. Only B-2 lymphocytes produce IgG whereas B-1 cells do not participate in the production of this Ig class. Using a novel synthetic all alpha(1-->3)-D-gluco configurated tetrasaccharide the Dex-specific B cells can for the first time be analyzed in FACS. In experiments using this newly designed low molecular Dex no signs of B cell apoptosis can be found. This demonstrates a true silencing of persisting Bgamma memory cells and supports previous by adoptive transfer experiments. In this suppression an involvement of CD28/B7-1 interaction can be demonstrated which is a necessary costimulatory suppression signal in addition to the cognate TCR/peptide-I-Ed interaction between J558 Id-specific T cells and J558 idiotype bearing B cells. This results in an activation of 178-4 Ts cells, leading to an overall suppression of the Dex-specific IgG isotype production on the one hand and on the other hand provides a signal for the survival and clonal expansion of J558 Id-positive B cells.

Animals↗
PubMed2000

The role of interleukin-4 in the regulation of sequential isotype switch from immunoglobulin G1 to immunoglobulin E antibody production.

The immunoglobulin (Ig)E immune response against protein antigens is profoundly influenced by the antigen dose used for immunization. Whereas immunization of CBA/J mice with low antigen doses results in the production of large amounts of IgE antibody, priming with high antigen doses leads to only marginal IgE antibody production in animals. However, in vitro restimulation of spleen cells from mice primed with high antigen doses leads to considerable activation of IgE-producing B cells, which suggests that B cells primed for IgE antibody production do exist among spleen cells. We investigated the modalities of activation of these memory B cells. The data presented here reveal that the anamnestic IgE immune response in vitro is strictly dependent on the presence of IgG1-expressing B cells, which differentiate after a sequential isotype switch into IgE-producing plasma cells with the help of primed CD4+ T cells. The induction of IgE-producing plasma cells requires a cognate interaction between B cells and CD4+ T cells. Interleukin (IL)-4 seems not to be involved in this process, since IgE production in vitro is resistant to suppression by anti-IL-4 monoclonal antibody. Finally, we show that IgG1-expressing B cells represent a relevant memory cell population in vivo also, but in contrast to the in vitro situation the final differentiation into IgE-producing plasma cells is dependent on IL-4.

Animals↗
PubMed1999

Involvement of CD28 cosignalling in the T cell-mediated suppression of the IgG antibody response against the TI-2 antigen alpha(1-->3) dextran.

The humoral immune response against alpha(1-->3) dextran (Dex) in BALB/c mice is characterized by the formation of predominantly IgM antibodies bearing the J558 idiotype. IgG antibodies do not appear in euthymic mice. In athymic animals, however, the response proceeds to a vigorous IgG production. In euthymic mice formation of IgG is suppressed by J558 idiotype specific regulatory T cells recognizing in association with I-Ed and in cognate T/B interaction the V(H) CDR3 derived peptide of the J558 idiotype. Only B-2 lymphocytes produce IgG whereas B-1 cells do not participate in the production of this Ig class. Using novel synthetic all alpha(1-->3)-D-gluco configured tetrasaccharide the Dex-specific B cells can for the first time be analyzed in FACS. In experiments using this newly designed low molecular Dex no signs of B cell apoptosis can be found. This demonstrates a true silencing of persisting Bgamma memory cells as previously suggested by adoptive transfer experiments. In this suppression a further involvement of CD28 and B7-1 interaction can be demonstrated which delivers a necessary costimulatory suppression signal in addition to the cognate TCR/peptide-I-Ed interaction between J558 specific T cells and J558 idiotype bearing B cells.

Animals↗
PubMed1998

Antigen dose-dependent differences in IgE antibody production are not due to polarization towards Th1 and Th2 cell subsets.

The quality of the humoral immune response against protein antigens in CBA/J mice is dependent on the antigen dose used for immunization: low doses induce high titers of IgE antibodies, whereas high doses promote the production of IgG2a antibodies but inhibit IgE formation. To investigate whether the reciprocal regulation of antibody production is possibly due to a differential activation of Th1 and Th2 cell populations in the two immunization groups, the cytokine pattern of spleen cells from both groups, cultured with antigen in vitro, was analyzed by measurement of intracellular and secreted cytokine levels. The data presented show that in vitro restimulated spleen cells from mice primed with low as well as with high doses of antigen produce predominantly the Th2 cytokines IL-4 and IL-10 but reduced levels of IL-12. The release of IFN-gamma is only slightly enhanced compared to unstimulated control cultures. The results indicate that CD4+ T cells in both groups belong mainly to the Th2 cell subset. This finding is contradictory to the general allegation that the antigen dose is decisive for the polarization of Th1 versus Th2 immune responses and shows that the antigen dose-dependent regulation of IgE antibody production is not due to differential polarization towards Th1 and Th2 cells.

Animals↗
PubMed1998

The J558 VH CDR3 region contributes little to antibody avidity; however, it is the recognition element for cognate T cell control of the alpha(1-->3) dextran-specific antibody response.

Analysis of the humoral immune response of BALB/c mice to alpha(1-->3) dextran (Dex) reveals novel aspects of T cell-mediated control of 'type 2 thymus-independent' responses against polysaccharide antigens. The IgM and IgG antibody response, dominated by the J558 idiotype (Id), is controlled by Id-specific T cells. These regulatory T cells, for which the T cell clone 178-4 Ts with characterized TCR alpha and beta chain sequences is the prototype, expand in all BALB/c mice upon immunization with Dex. They suppress in a cognate interaction the expansion of J558 Id-bearing B cells, committed for production of IgG antibodies. Furthermore they provide a gate which precludes variability in the VH CDR3 region of IgG antibodies appearing occasionally in the periphery. The VH CDR3 region is the recognition element of 178-4 Ts analogous T cells but contributes little to affinity for the antigen. For recognition by 178-4 Ts cells not even minimal sequence deviations of the J558 Id peptide are allowed. The tight germline programmed complementarity between J558 Id-bearing Dex-specific B and J558 Id-specific 178-4 Ts analogous T cells leaves little room on both sides for ontogenetic variability.

Amino Acid Sequence↗
PubMed1998

Differential activation of CD8+ tumor-specific Tc1 and Tc2 cells by an IL-10-producing murine plasmacytoma.

The involvement of counteractive CD8+ T-cell subsets during tumor-specific immune responses was analyzed in a syngeneic murine plasmacytoma model. CD8+ Tc cells against the immunogenic IL-10-producing BALB/c plasmacytoma ADJ-PC-5 can be easily induced by immunization of BALB/c mice with X-irradiated ADJ-PC-5 tumor cells in vivo and in vitro. However, the failure of recipient mice to mount a protective Tc response against the tumor during early stages of a real or simulated tumor growth is not due to immunological ignorance, but depends on the induction of tumor-specific tolerance, involving a population of tumor-induced CD8+ T cells that are able to inhibit the generation of tumor-specific Tc cells in a primary ADJ-PC-5-specific MLTC, using IFN-gamma as a suppressive factor. Whereas most long-term cultivated CD8+ ADJ-PC-5-specific Tc lines produce type-1 cytokines on stimulation, at least two of them, which were derived from a primary MLTC, display a type-2 cytokine spectrum. Furthermore, the primary in vitro Tc response against ADJ-PC-5 cells shows characteristics of a Tc2 response. The Tc response is strictly depending on tumor-derived IL-10. CD8+ Tc cells that are induced in a primary MLTC do not produce IFN-gamma, and the tumor-specific Tc response is enhanced by IL-4 but suppressed by IFN-gamma or IL-12. In contrast, ADJ-PC-5-specific CD8+ Tc cells from immunized mice are IFN-gamma producing Tc1 cells. Since the primary in vitro Tc response against the tumor is suppressed even by the smallest numbers of irradiated ADJ-PC-5-specific Tc1 cells via IFN-gamma, these Tc1 cells behave similar to the suppressive CD8+ T cells that are induced during early stages of ADJ-PC-5 tumorigenesis.

Animals↗
PubMed1997

CD8+ tumor-specific Tc cells primed in vivo or in vitro against the BALB/c plasmacytoma ADJ-PC-5 use the same TcR V beta families but display distinct TC1 or TC2 characteristics.

The involvement of counteractive CD8+ T cell subsets in tumor-specific unresponsiveness was analyzed in a syngeneic murine tumor model. CD8+ cytotoxic T cells against the IL-10 producing BALB/c plasmacytoma ADJ-PC-5 can be easily induced in vitro, in a primary syngeneic mixed lymphocyte tumor cell culture (MLTC), or in vivo, by repeated immunization of syngeneic BALB/c mice with high doses of X-irradiated ADJ-PC-5 tumor cells. Long term cultivated CD8+ ADJ-PC-5-specific Tc lines use either TcR of the V beta 6 or V beta 8.1/8.2 type, irrespective if the lines were derived from a primary MLTC or from immunized mice. While most of the Tc lines produce type-1 cytokines (IFN-gamma, no IL-4) upon stimulation, at least two of them, which were derived from a primary MLTC, display a type-2 cytokine spectrum (IL-4, no IFN-gamma). The primary in vitro Tc response against ADJ-PC-5 cells shows characteristics of a TC2 response: CD8+ Tc cells which are induced in a primary MLTC do not produce IFN-gamma, and the tumor-specific Tc response is enhanced by IL-4 but suppressed by IFN-gamma or IL-12. In contrast, ADJ-PC-5-specific CD8+ Tc cells from immunized mice are IFN-gamma producing TC1 cells. Since the primary in vitro Tc response against the tumor is suppressed even by lowest numbers of irradiated ADJ-PC-5-specific TC1 cells via IFN-gamma, these TC1 cells behave similar to a previously described regulatory subset of IFN-gamma producing CD8+ T cells, which are induced during early stages of ADJ-PC-5 tumorigenesis and inhibit the induction of a tumor-specific Tc response from naive BALB/c spleen cells in vitro.

Adjuvants, Immunologic↗
PubMed1997

Antigen dose-dependent predominance of either direct or sequential switch in IgE antibody responses.

Priming of CBA/J mice with minute doses of protein antigens (Ag) leads to high IgE antibody (Ab) titres in the immune sera of these animals. In contrast priming with large doses elicits only a marginal production of IgE Ab. In vitro restimulation of spleen cells from animals primed with large doses and lacking in vivo IgE Ab leads to a burst of IgE Ab-forming cells. This in vitro anamnestic response is lacking in mice primed with minute doses of Ag. In order to trace the cellular basis of the in vitro IgE memory response we have extended the analysis of the distribution of Ab isotypes to Ag-primed IgG1-deficient delta 5'S gamma 1 mice. The data presented here must be interpreted as followed. Priming of mice with minute doses of Ag leads to a direct switch from IgM to IgE Ab expression in both strains. These animals have high IgE Ab titres without establishing an IgE memory. The direct switch was verified by polymerase chain reaction and Southern blot analysis of switch circle DNA isolated from Ag-specific B cells of CBA/J mice primed with minute doses of Ag. In contrast to immunization with minute doses, priming with large doses of Ag fails to induce in vivo IgE Ab production in CBA/J and delta 5'S gamma 1 mice but establishes a B epsilon memory in CBA/J mice which involves IgG1-bearing intermediate B cells. In vivo these B epsilon memory cells do not enter the status of IgE Ab-producing cells. In vitro they can be released from this anergy and presumed suppression and develop in an anamnestic response into a large population of IgE Ab-forming B cells. This increase in the number of IgE Ab-producing cells after restimulation in vitro is lacking in delta 5'S gamma 1 mice, apparently because of their inability to generate IgG1-expressing precursor cells. The notion of a sequential switch and an IgG1 intermediate B epsilon memory status is also supported by depletion and inhibition experiments. Elimination of IgG1-expressing B cells in CBA/J mice primed with high doses of Ag prevents the IgE Ab burst after in vitro challenge with Ag. The data further suggest that the two switch pathways are not mutually exclusive and that the Ag dose can decide which pathway is preferentially used.

Animals↗
PubMed1997

The murine (H-2k) T-cell epitopes of bee venom phospholipase A2 Lie outside the active site of the enzyme. Implications with respect to a paracrine activation of Th2 cells for an IgE antibody response.

Recombinant, enzymatic active phospholipase A2 from bee venom (PLA2) is a potent inducer of IgE antibody formation in CBA/J (H-2k) mice. In contrast, a recombinant mutant protein lacking enzymatic activity due to an amino acid exchange in the active site of the enzyme fails to induce IgE antibodies under identical immunization conditions. Peptide mapping and T-cell stimulation experiments with 18-mer overlapping peptides locate the T-helper cell-activating epitopes in the C-terminal region of the PLA2 protein. No T-cell epitopes are found in the area around position 34, the center of the enzymatically active site. The data support a model in which initially an enzymatic activation of mast cells or basophiles leads to IL-4 production which in a paracrine way drives T-helper cells, concomitantly activated by antigen, into Th2 differentiation. This ultimately favors B-cell activation for an IgE response.

Amino Acid Sequence↗
PubMed1996

Suppression of tumour-specific cytotoxic T-cell responses against the syngeneic BALB/c plasmacytoma ADJ-PC-5 by tumour-induced CD8+ regulatory T cells via IFN-gamma.

The mechanisms of tolerance induction by tumour cells during early stages of tumourigenesis were analysed in a murine model system using the highly immunogenic BALB/c plasmacytoma ADJ-PC-5. Early stages of tumourigenesis were simulated in syngeneic BALB/c mice by repeated intraperitoneal injections with subimmunogenic doses of X-irradiated ADJ-PC-5 tumour cells. This treatment causes a state of tumour-specific tolerance in a high percentage of mice, involving a population of CD8+ peritoneal T cells which are able to suppress a protective tumour-specific Tc response against this tumour. Using a primary mixed lymphocyte tumour cell culture (MLTC) as an in vitro system to study suppressive mechanisms of such regulatory T cells, the role of production or consumption of a number of cytokines was analysed. The data presented here demonstrate that inhibition of a protective Tc response against ADJ-PC-5 tumour cells is due to IFN-gamma production by suppressive T cells from tolerized mice, but not to IL-2 consumption. In contrast to typical CD8+ Tc cells, ADJ-PC-5-specific CD8+ Tc cells do not produce IFN-gamma and are furthermore suppressed by IFN-gamma. Thus, tumour-induced suppressive T cells and tumour-specific Tc cells seem to represent functionally and phenotypically different subsets of CD8+ T cells, possibly pointing towards a differential activation of type-1 and type-2 CD8+ T cells depending on the dose of tumour cells.

Animals↗
PubMed1995

Proteoglycan form of colony-stimulating factor-1 (proteoglycan-100). Stimulation of activity by glycosaminoglycan removal and proteolytic processing.

A proteoglycan had been isolated from the conditioned media of a human osteosarcoma cell line and had tentatively been named proteoglycan-100 (PG-100) because of the size of its core glycoprotein. Amino acid sequencing of the purified proteoglycan and cDNA analysis were consistent with the assumption that PG-100 is identical with the proteoglycan form of CSF-1 (or macrophage colony-stimulating factor). PG-100 induced mouse macrophage differentiation. Proliferation of macrophages was stimulated in a dose-dependent manner. On a molar basis, however, about 100- to 300-fold higher doses of PG-100 than of recombinant human (rh)CSF-1 were required for the half-maximal growth-stimulating effect. Upon enzymatic removal of the glycosaminoglycan chain, the purified core protein exhibited higher activity, but was still about 20-fold less active than rhCSF-1. Incubation of the purified proteoglycan for 48 h at 37 degrees C led to the formation of a glycosaminoglycan-free 50-kDa fragment either by autoproteolysis or by the action of a protease not yet identified. The purified fragment exhibited almost the same biologic activity as rhCSF-1. The glycosaminoglycan chain of the growth factor was not only shown to inhibit CSF-1 activity but also to increase the stability of the core protein when the CSF-1-producing osteosarcoma cells were maintained in a collagen lattice. These findings provide a link between a soluble, highly active cytokine and its extracellular matrix storage form of comparatively low activity.

Amino Acid Sequence↗
PubMed1995

Regulation of an anti-polysaccharide immune response in BALB/c mice through a tight T and B lymphocyte idiotypic connection.

The isotype expression in the J558 idiotype-associated humoral immune response against alpha(1-->3)-dextran in BALB/c mice is controlled by idiotype-specific T cells which silence in situ B lymphocytes primed and committed to an IgG response. This leads to a restriction of the type II thymus-independent response to the sole production of IgM antibodies. The availability of the T cell receptor (TcR) alpha and beta sequences for such a regulatory T cell clone allows the investigation of the degree of heterogeneity of the TcR usage of these T cells. It is found that all alpha(1-->3)-dextran-primed BALB/c mice use a very similar, possibly identical TcR. This suggests a tight, possibly genetically programmed, interaction between the J558 idiotype-bearing dextran-specific B cells and their idiotype-specific regulatory T cell counterparts.

Animals↗
PubMed1995

Interleukin-12 profoundly up-regulates the synthesis of antigen-specific complement-fixing IgG2a, IgG2b and IgG3 antibody subclasses in vivo.

The influence of the cytokine interleukin-12 (IL-12) on humoral immune responses was studied in vivo. CBA/J mice immunized with protein antigens (keyhole limpet hemocyanin, phospholipase A2) adsorbed to aluminum hydroxide (Alum) develop a Th2-like immune response characterized by the production of large amounts of IgG1 as well as some IgE but little IgG2a, IgG2b and IgG3 antibodies. IL-12 is a cytokine that promotes the development and the activation of Th1 cells. Th1 cells are involved in the induction of cellular immunity, which is characterized by low or absent antibody production. On the other hand, some Th1-like immune responses are associated with a strong antibody production of the IgG2a, IgG2b and IgG3 subclasses. Thus, we investigated whether treatment with IL-12 would down-regulate the humoral immune response or stimulate antibody production of the IgG2a, IgG2b and IgG3 subclasses. We observed that: 1) administration of IL-12 to mice together with protein antigens adsorbed to Alum strongly enhanced the humoral immune response by increasing the synthesis of antigen-specific antibodies of the IgG2a, IgG2b and IgG3 subclasses 10- to 1000-fold. The synthesis of IgG1 was not or only slightly (2-5-fold) enhanced, whereas that of the IgE isotype was suppressed. 2) These effects of IL-12 were observed when high (10 micrograms, 100 micrograms) or low doses (0.1 microgram) of antigen were used for immunization. 3) Titration of IL-12 in vitro revealed that IgG2a is strongly up-regulated over a wide dose range of IL-12 (10 to 1000 ng/day). 4) The effects of IL-12 in vivo are at least partially interferon (IFN)-gamma-dependent because an anti-IFN-gamma mAb in combination with IL-12 prevented most of the enhanced IgG2a production. 5) Mice receiving IL-12 showed a strong up-regulation of IFN-gamma but no inhibition of IL-5 synthesis by spleen cells activated ex vivo with antigen. These results suggest that IL-12 is a potent adjuvant for enhancing humoral immunity to protein antigens adsorbed to Alum, primarily by inducing the synthesis of the complement-fixing IgG subclasses 2a, 2b and 3.

Aluminum Hydroxide↗
PubMed1995

Administration of IL-12 during ongoing immune responses fails to permanently suppress and can even enhance the synthesis of antigen-specific IgE.

The synthesis of antibodies of the IgE isotype in mice largely depends on IL-4, a cytokine that is released by T lymphocytes of the Th2 subtype. IL-12 is a cytokine considered to direct Th cell development into a Th1 direction and to suppress Th2 responses including the synthesis of IgE. Here we report about the influence of IL-12 on the IgE responses of mice immunized with protein antigens adsorbed to aluminum hydroxide. To avoid problems with the detection of IgE caused by an excess of competitive IgG antibodies produced in IL-12-treated mice, serum IgE was first extracted from the serum by plate-bound anti-IgE mAb and then determined either as total IgE or as antigen-specific IgE by using biotinylated anti-IgE or biotinylated antigen. Depending on the strain of mice and the dose of IL-12 injected together with the antigen, IL-12 can either temporarily suppress or augment the synthesis of (antigen-specific) IgE antibodies. This applies for CBA/J mice immunized six times in biweekly intervals with minute (0.1 micrograms/injection) or three-times with large (5 micrograms/injection) amounts of the bee venom allergen phospholipase A2 (PLA2). Under both conditions the antibody response is characterized by the production of predominantly IgG1 as well as IgE but very little IgG2a, IgG2b and IgG3 antibodies. Simultaneous application of low doses of IL-12 (1 or 10 ng/day) led to a 2- to 4-fold enhancement of IgE production (PLA2-specific IgE or total IgE). Only a high dose of 1 micrograms IL-12/day resulted in a 3- to 10-fold reduction of the IgE response. This suppression was not stable, however, because the synthesis of IgE antibodies was stimulated to a high level when these mice subsequently received a second course of immunizations in the absence of IL-12. Likewise, the synthesis of IgE was only temporarily suppressed by IL-12 treatment in CBA/J mice immunized with keyhole limpet hemocyanin (KLH) as antigen. However, application of low (10 ng/day) or high (1 microgram/day) doses of IL-12 during the primary course of immunizations of CBA/J mice with KLH suppressed the IgE response slightly or strongly respectively. In striking contrast, the KLH-specific IgE response of BALB/c mice was upregulated even when high doses of IL-12 (1 microgram/day) were injected simultaneously with the immunizations. Thus, these results demonstrate a great variability regarding the influence of IL-12 treatment on ongoing IgE responses in vivo.

Animals↗
PubMed1995

In situ dormancy of B lymphocytes programmed for an IgE antibody response and their sudden release from unresponsiveness under in vitro conditions.

Priming of CBA/J mice with different doses of antigen has a profound effect on the ratio of IgE versus IgG antibodies appearing upon immunization. Repeated injections of minute doses induce IgG and high titers of IgE antibodies. Large doses elicit a high IgG but a very low IgE antibody titer. In order to study the modalities for activation and inactivation of IgE-producing B cells, an in vitro culture system was established in which spleen cells from animals primed with keyhole limpet hemocyanin were re-stimulated with antigen. In contrast to the expectation from the in vivo situation, spleen cells from animals immunized with large doses of antigen and virtually lacking IgE antibodies produce high amounts of IgE antibodies upon re-stimulation in vitro. The titers in spleen cell cultures from mice primed with minute doses remain proportional to the response measured as serum antibodies. In accordance with the induction of high amounts of IgE antibodies in spleen cell cultures from mice primed with large doses, the frequency of IgE antibody-secreting cells was raised drastically, approximately 1000-fold. The in vitro response is a true anamnestic response. The sudden appearance in high frequency of IgE antibody-forming cells among spleen cells isolated from primed mice which have high IgG but virtually no IgE antibody titers is as yet unexplained and the origin of the B epsilon memory cells has not yet been traced. The answer might be crucial for our understanding of the down-regulation of the IgE immune responses.

Animals↗