Abstract Background : T helper 2 cell type cytokines, such as interleukin (IL)‐4 and IL‐5, play pivotal roles in the development of allergic diseases. However, the mechanism by which naive CD4 + T cells acquire the ability to produce these cytokines remains unclear. Recently, it was reported that IL‐7 induces the ability to produce IL‐4 as well as interferon (IFN)‐γ and IL‐5 in naive CD4 + T cells without TCR stimulation. To further analyze the mechanism of acquiring IL‐4‐producing ability by naive CD4 + T cells, the effects of IL‐7 on human cord blood CD4 + T cells were compared with those of IL‐4, which induced the ability to produce IFN‐γ but not IL‐4. Results : Interleukin‐7 preserved the population of CD4 + CD31 – T cells in cord blood and induced their IL‐4‐producing ability without T cell receptor (TCR) stimulation, while IL‐4 induced CD31 on CD31 – T cells and could not induce their IL‐4‐producing ability. Both the CD31‐inducing effect and the inhibitory priming effect for IL‐4‐production by IL‐4 were also observed after cord blood CD4 + T cells had been primed with IL‐7 and acquired the IL‐4‐producing ability. Conclusions : Interleukin‐7 induced the IL‐4‐producing ability in naive CD4 + CD31 – T cells without TCR stimulation, suggesting that the signal transduction via CD31 may have an inhibitory effect on the acquisition of the IL‐4‐producing ability by cord blood CD4 + T cells in the absence of TCR stimulation.
Stimulation with specific pairs of anti-CD2 antibodies can induce T cell activation and proliferation. In this study, we investigate the significance of ZAP-70 in CD2 signaling using ZAP-70-deficient T cells derived from a CD8-deficient patient and show that ZAP-70 is necessary for cellular proliferation and cytokine production in T cells stimulated via CD2. Biochemical analyses show that CD2 stimulation induces activation of mitogen-activated protein kinase (MAPK) superfamily in ZAP-70-deficient T cells, indicating that a ZAP-70-independent pathway(s) exists for MAPK superfamily activation via CD2. In contrast, intracellular Ca2+ mobilization and activation of nuclear factor of activated T cells (NFAT) upon CD2 triggering were impaired in T cells lacking ZAP-70. Furthermore, we found that pharmacological Ca2+ elevation combined with CD2 stimulation restored NFAT activation and subsequent cytokine production in ZAP-70-deficient T cells. These results indicate that in CD2 signaling, ZAP-70 plays an essential role in Ca2+ mobilization and NFAT activation.
Cross-linking of surface IgM and surface IgD by anti-IgM antibodies and anti-IgD antibodies, respectively, showed different effects on the growth of normal human peripheral blood B cells and the human B lymphoma cell line, B104. Only cross-linking of surface IgM transduced signals that inhibited cell division of peripheral blood B cells and B104 cells at the G2/M interphase. In B104 cells, the inhibition of cell division was followed by rapid B104 cell death. The negative signals were inhibited by cyclosporin A and FK-506 at lower concentrations than those that inhibited proliferation of the B cells. Anti-IgM antibody-induced B104 cell death was dependent on CA 2÷ influx and macromolecular synthesis. B104 cells treated with anti-IgM antibodies showed neither DNA fragmentation or morphology of apoptosis but showed DNA single-strand breaks and morphology of necrosis. Nicotinamide inhibited anti-IgM antibody-induced B104 cell death and the involvement of poly(adenosine diphosphate-ribosyl)ation was suggested in the process of the B104 cell death. With regard to the intracellular mechanisms responsible for the different signals, however, no qualitative difference was detected in putative signal transducers, including tyrosine phosphorylated protein, phosphatidyl inositol turnover, Ca 2+ influx, activation of protein kinase C, and messenger ribonucleic acid expression of c-los and Egr-1 when surface IgM and surface IgD were crosslinked. Further investigations of the mechanisms responsible for the different signals transduced through surface IgM and surface lgD will provide better understanding of immunodeficiencies and autoimmune diseases. (J ALLERGY CLIN IMMUNOL 1994;94:612-9.)
A human eosinophilic leukemia cell line, EoL-1, stopped proliferating at the G1 phase, differentiated into eosinophilic granule-containing cells, and died by apoptosis when stimulated with dibutyryl cyclic AMP (dbcAMP). To clarify the effects of dbcAMP, the effects of butyrate and cAMP-increasing reagents, prostaglandin E2 (PGE2) and forskolin, on EoL-1 cellular differentiation and apoptosis were examined and compared. PGE2 and forskolin but not butyrate induced differentiation to eosinophilic granule-containing cells, suggesting that cAMP played a primary role in eosinophilic differentiation of EoL-1 cells. PGE2, forskolin and butyrate, when used alone, did not induce apoptosis of EoL-1 cells significantly at the concentrations used, but sequential stimulation of EoL-1 cells with the cAMP-increasing reagents and butyrate showed that butyrate induced further maturation and apoptosis of cAMP-induced eosinophilic granule-containing cells. These results showed that cAMP and butyrate have different effects on eosinophilic differentiation and apoptosis of EoL-1 cells. The cAMP-increasing reagents and butyrate also showed different effects on expression of members of the bcl-2 family; PGE2 decreased bcl-2 and bax levels, whereas butyrate increased the bcl-2 level. PGE2 or PGE2+butyrate, but not butyrate alone, induced bcl-XS expression. EoL-1 cells constitutively expressed Fas and anti-Fas antibody induced EoL-1 cell death, but the Fas/Fas ligand system was not involved in dbcAMP-induced EoL-1 cell apoptosis. The EoL-1 cell line is thus a useful model in which to examine differentiation and apoptosis of eosinophilic leukemia cells.
Stimulation with specific pairs of anti-CD2 antibodies can induce T cell activation and proliferation. In this study, we investigate the significance of ZAP-70 in CD2 signaling using ZAP-70-deficient T cells derived from a CD8-deficient patient and show that ZAP-70 is necessary for cellular proliferation and cytokine production in T cells stimulated via CD2. Biochemical analyses show that CD2 stimulation induces activation of mitogen-activated protein kinase (MAPK) superfamily in ZAP-70-deficient T cells, indicating that a ZAP-70-independent pathway(s) exists for MAPK superfamily activation via CD2. In contrast, intracellular Ca2+ mobilization and activation of nuclear factor of activated T cells (NFAT) upon CD2 triggering were impaired in T cells lacking ZAP-70. Furthermore, we found that pharmacological Ca2+ elevation combined with CD2 stimulation restored NFAT activation and subsequent cytokine production in ZAP-70-deficient T cells. These results indicate that in CD2 signaling, ZAP-70 plays an essential role in Ca2+ mobilization and NFAT activation.
