Reactivity of Ly-2+ T cells against 2,4,6-trinitrophenyl (TNP)-modified syngeneic stimulator cells: specificity, frequency of interleukin 2-producing Ly-2+ helper T cells and clonal segregation from Ly-2+ cytotoxic T lymphocytes

IL-2, -4, and -15 differentially regulate O-glycan branching and P-selectin ligand formation in activated CD8 T cells

The glycosyltransferase core 2 beta1-6 N-acetylglucosaminyl transferase (C2GnT1 or C2GlcNAcT1) is responsible for formation of branched structures on O-glycans present on cell surface glycoproteins. The O-glycan branch created by C2GnT1 is physiologically important insofar as only this structure can be extended and modified to yield P-selectin ligands that promote initial interactions between extravasating lymphocytes and endothelia. In mature T cells, C2GnT1 activity is thought to be induced as an intrinsic consequence of T cell activation. Through analysis of C2GnT1-dependent epitopes on CD43 and CD45RB we have found that in activated CD8(+) T cells expression of C2GnT1 was dependent upon exposure to specific cytokines rather than being induced as a direct consequence of activation. Activated CD8(+) cells became receptive to strong induction of C2GnT1 expression and P-selectin ligand expression in response to IL-2, moderate induction by IL-15, and minimal induction in response to IL-4. Our observations clarify the relationship between T cell activation and C2GnT1 expression, demonstrate the differential impact of distinct cytokines on expression of C2GnT1 activity and P-selectin ligand, and reinforce the concept that the cytokine milieu subsequent to activation can influence adhesion systems that dictate lymphocyte homing properties.

Helper interleukins are produced by both CD4 and CD8 splenic T cells after mitogen stimulation

We have earlier described (Cardell, S. and Sander, B., Eur. J. Immunol. 1990. 20:389) mitogen-induced production of interleukin (IL)2, IL4 and IL5 mRNA by murine spleen cells, analyzed by in situ hybridization. In the present study we have investigated the potential of CD8 T cells to produce these interleukins, normally associated with the helper function of CD4 T cells. When concanavalin A (Con A)-activated spleen cells were restimulated with Con A and phorbol 12-myristate 13-acetate (PMA), higher levels of IL2, IL4 and IL5 mRNA were induced, as detected both by increased frequencies of positive cells, and by more mRNA per cell. Four-to-six-day Con A blasts were enriched for CD4+ or CD8+ T cells, and restimulated with Con A and PMA. Both CD4 and CD8 cells were found to produce all three kinds of mRNA when restimulated. The frequencies of IL2 mRNA-containing CD8 cells were half of those found for CD4 cells (3.5% as compared to 7%). On the average 1% of the CD8 cells were induced to produce IL4 and IL5 mRNA, while 9% and 3% of the activated CD4 cells contained IL4 and IL5 mRNA, respectively. CD4 and CD8 cells displayed different sensitivities to the reagents when tested alone. Con A induced the synthesis of IL4 and IL5 in CD4 cells, but not CD8 cells, independently of PMA. PMA alone induced extensive thymidine incorporation in CD8 cells, but not in CD4 cells, in the absence of detectable lymphokine mRNA. The results suggest that some CD8 cells have the capacity to give help in immune responses, by secretion of IL2, IL4 and IL5.

Dissection of signals controlling T cell function and activation: H7, an inhibitor of protein kinase C, blocks induction of primary T cell proliferation by suppressing interleukin (IL)2 receptor expression without affecting IL2 production

T cell activation induced via cross-linking of the T cell receptor (TcR) stimulates hydrolysis of phosphatidylinositol to the second messengers diacylglycerol (DAG) and inositol 1,4,5-triphosphate (IP3). DAG is necessary for the activation and function of protein kinase C (PKC) which is suggested to play a key role in the cascade of signal transduction when translocated from the cytosol to the cell membrane. In this report, we investigated responses of resting vs. activated Ly-2+ and L3T4+ T lymphocytes in the presence of the PKC inhibitor H7 [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine]. H7 inhibited the induction of primary T cell proliferation, while interleukin 2 (IL 2) production was fully retained. The effect of the PKC inhibitor on primary T cells depended on the type of ligand interacting with the TcR: increasing doses of concanavalin A or of immobilized anti-CD3 monoclonal antibody (mAb), but not of anti-V beta 8 or of anti-TcR alpha/beta mAb, partly overcame the blockade, indicating a differential signaling compared to the former stimuli. The blockade of T cell proliferation by H7 was not due to an inhibition of PKC translocation, but occurred even 4-8 h after T cell induction and correlated with a significant reduction of IL 2 receptor (IL 2R) expression. In contrast, the mRNA levels of IL 2R and the cellular proto-oncogenes c-fos and c-myc were not affected. On activated T cells, H7 neither blocked proliferation nor IL2R expression. Consequently, H7 dissects the signal resulting in T cell proliferation from those governing the triggering of other T cell functions, i.e. IL 2 production, during primary responses of Ly-2+ or L3T4+ murine T lymphocytes.

Effect of cyclosporin A on T cell immunity. I. Dose-dependent suppression of different murine T helper cell pathways

Cyclosporin A (CsA) is used as a clinical immunosuppressive agent. Despite its immunosuppressive potential, some studies involving in vivo administration of cyclosporin have failed to verify the immunosuppressive activity of this agent. The present study investigates the effect of different concentrations of CsA added in vitro, or of different doses of CsA administered in vivo, on the ability of murine spleen cells to produce interleukin 2 and to generate cytotoxic T lymphocytes in vitro when stimulated with TNP-self or H-2 alloantigens. The results indicate that self Ia-restricted T helper (Th) cells are more sensitive to lower doses of CsA than Th cells that are allorestricted. Thus, doses of CsA were found (15-30 mg/kg) that inactivated self Ia-restricted Th function, but not other Th or effector function. This Th cell defect could be partially corrected in vitro by addition of Th cell factors to the sensitization cultures. A higher dose (75 mg/kg) of CsA inactivated all detectable T cell responses, and this defect was not corrected by addition of Th cell factors. T cell function returned to normal levels within two weeks of cessation of CsA at all three doses of CsA tested. The selective loss of L3T4 Th function at the lower doses of CsA was associated with a radiosensitive, Ly-2 suppressor T cell that was selective in its action on self Ia-restricted Th cell function. Loss of all T cell function at the higher dose of CsA was associated with a radioresistant non-T suppressor cell that inactivated all T cell function tested. These results are discussed with respect to the selective dose-dependent effects of CsA on Th subsets, on the activation of suppressor cells with similar selectivity, and the implications of these findings on the use of CsA to prevent rejection of tissue allografts.