CD23/Fc epsilon RII expression on phytohemagglutinin-A- or phorbol-12myristate-13acetate-Ca(2+)-activated human tonsil T cells

Changes in ribosomal binding activity of eIF3 correlate with increased translation rates during activation of T lymphocytes

The rate of protein synthesis in quiescent peripheral blood T lymphocytes increases dramatically following mitogenic activation. The stimulation of translation is due to an increase in the rate of initiation caused by the regulation of initiation factor activities. Here, we focus on eIF3, a large multiprotein complex that plays a central role in the formation of the 40 S initiation complex. Using sucrose density gradient centrifugation to analyze ribosome complexes, we find that most eIF3 is not bound to 40 S ribosomal subunits in unactivated T lymphocytes but becomes ribosome-bound following activation. Immunoblot analyses of sucrose gradient fractions for individual eIF3 subunits show that the small eIF3j subunit is unassociated with the eIF3 complex in quiescent T lymphocytes, but upon activation joins the other eIF3 subunits and binds 40 S ribosomal subunits. Because eIF3j has been shown to be required for eIF3 binding to 40 S ribosomes in vitro, the results suggest that mitogenic stimulation of T lymphocytes leads to an activation of eIF3j, thereby enabling eIF3 to bind to the larger ribosome-free eIF3 subunit complex, and then to the 40 S ribosomes. The association of eIF3j with the other eIF3 subunits appears to be inhibited by rapamycin, suggesting a mechanism that lies downstream from the mammalian target of rapamycin kinase. This association requires ionomycin together with a phorbol ester, which also suggests that calcium signaling is involved. We conclude that the complex formation of eIF3 and its association with the ribosomes might contribute to increased translation rates during T lymphocyte activation.

Distinct modulation by interferon-gamma (IFN-gamma) of CD23 expression on B and T lymphocytes of atopic subjects

The low-affinity IgE receptor (FcepsilonRII/CD23) plays a role in IgE production. Cytokines participating in IgE synthesis also modulate CD23 expression on lymphocytes, but whether this modulation is different in atopic subjects remains unclear. We studied CD23 expression on B and T lymphocytes in 10 asthmatic patients with Dermatophagoides pteronyssinus hypersensitivity and 10 healthy non-atopic subjects. Studies were performed by flow cytometry, in phytohaemagglutinin (PHA) or IL-4-stimulated mononuclear cell cultures, alone or in the presence of IFN-gamma. Soluble CD23 (sCD23) released in the culture supernatants was measured by enzyme-linked immunoassay. Both PHA and IL-4 induced the expression of CD23 on lymphocytes of atopic and non-atopic subjects. Whereas PHA increased both the percentage and mean fluorescence intensity of CD23+ B and T cells, IL-4 alone did not increase the percentage of CD23+ T cells. The effects of IFN-gamma were different in both groups, since it was able to reduce the percentage of PHA-stimulated CD23+ T cells only in non-atopic individuals. In non-atopic subjects more than atopic, levels of sCD23 were increased in the supernatants of PHA and IL-4 cultures. These results show that the modulation of CD23 expression is different on B and T cells, and that IFN-gamma acts differently in atopic and non-atopic individuals.

Regulation of human cytotoxic T lymphocytes development by the synergistic effect of IL-7 and sCD23

The present study was undertaken to investigate the interaction of IL-7 and sCD23 on human peripheral blood T cell activation and CTL differentiation. Purified T lymphocytes were stimulated with mitogen plus IL-2 and subcultured for 7 days with IL-7 and/or sCD23. The combination of IL-7 and sCD23 synergistically enhanced the proliferation of both CD4+ and CD8+. T cells. CD8+ T cells, however, were usually more responsive to IL-7 and sCD23. This synergy was observed on both subsets of T cells. Furthermore, these cytokines synergistically augment the CTL activity of CD8+ T cells in both mitogen- and antigen-activated T cells. MAbs anti-IL-2 or anti-IL-2R (CD25) and anti-IL-12 had no effect on T cell proliferation and CD8+ cytotoxic activity induced by IL-7 and sCD23. We analyzed the effect on IFN-gamma induction by CD8+ T cells and found that IL-7 alone was incapable of inducing detectable levels of IFN-gamma production, but together with sCD23 it enhanced the production of IFN-gamma. We also found that IFN-gamma was not required for enhanced CTL activity of CD8+ T cells, because rabbit anti-IFN-gamma did not block the synergistic effects of either cytokine. The data demonstrate that the synergistic stimulatory activity of IL-7 and sCD23 may be of significance in the human CTL development and provide an alternative mechanism of stimulating T cells for use in immunotherapy.

The effect of disodium cromoglycate (DSCG) on in vitro proliferation of CD4+, CD8+, and CD19+ cell populations derived from allergic and healthy donors

The effect of disodium cromoglycate (DSCG) on in vitro proliferation of CD4+ and CD8+ T cells and CD19+ B cells, positively selected by immunomagnetic separation, was investigated. The cells were obtained from allergic patients with moderate serum IgE levels and mild to moderate atopic dermatitis, and healthy controls. The different cell subfractions were stimulated with mitogens or specific allergens, as well as cell supernatants from the lymphoblastoid B- (RPMI 8866) and T-hybridoma (166 A2) cell lines. Proliferative responses of T- and B-cell subsets stimulated with mitogens together with recombinant interleukin-2 (rIL-2) or accessory cells (AC) could be inhibited by DSCG. In allergic individuals, significant allergen-specific stimulation could be observed in the CD8-depleted peripheral blood mononuclear cell (PBMC) fractions. Isolated CD4+ T cells, without AC or IL-2, could also be stimulated with specific allergen, but the responses were rather low. DSCG inhibited, concentration dependently, all allergen-induced responses. Interestingly, only atopic derived CD4+ and CD8+ T cells were stimulated by soluble low-affinity IgE receptor (Fc epsilon RII/sCD23) and IgE binding factor (IgEBF), including IgE enhancing factor, present in culture supernatants from RPMI 8866 and 166 A2, respectively. These responses were also inhibited by DSCG. This was in contrast to the amplifying effect of DSCG on spontaneously proliferating RPMI 8866 and 166 A2 cells, cultured in fresh cRPMI 1640 medium without sCD23 and IgE enhancing factor. Our results show that DSCG delivers an inhibitory signal or signals to PBMC subpopulations expressing Fc epsilon RII/sCD23, either upregulated by phytohemagglutinin in normal and atopic cells, or by allergens or sCD23 in atopic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of H1 receptor antagonists on peripheral blood mononuclear cells, adenoid cells and primary cell lines

This study describes the in vitro effect of three H1 receptor antagonists (dexchlorpheniramine, terfenadine and loratadine) on human peripheral blood mononuclear cells (PBMC, n = 30) from allergic patients and healthy individuals. The three H1 receptor antagonists significantly inhibited antigen/mitogen-induced PBMC proliferation in a concentration-dependent manner. Allergen-specific T-cell responses in allergic individuals were similarly inhibited. The effect of the three drugs was also tested in cultures of mononuclear cells derived from adenoid tissue. The growth kinetics were investigated using spontaneously proliferating cell lines to examine whether the inhibition was caused by general toxicity. Three cell lines, HCT 8 (an ileocaecal adenocarcinoma) RPMI 8866 (B-cell line) and 166 A2 (T hybridoma) were tested. Loratadine (< 0.03 microM) and dexchlorpheniramine (< 0.62 microM) altered the kinetics of HCT 8 and RPMI 8866, respectively. When testing RPMI 8866 and 166 A2, the growth-inhibitory effect of terfenadine and loratadine could be neutralized by addition of cell culture filtrate from RPMI 8866 or 166 A2. These culture filtrates are rich in soluble low-affinity IgE receptor (sCD23) and IgE-binding factor (IgEBF), respectively. Our findings show that the antihistamines investigated display some non-convential in vitro anti-allergic properties possibly not related to their interaction with the H1 receptor. In addition, our results suggest: a) The H1 receptor antagonists used differ in their pattern of cell inhibition; b) The inhibitory effect is completely reversible at low drug concentrations.