Multiple pathways for antigen-independent activation of a T helper hybridoma

The in vitro effect of Pidotimod on some immune functions in cancer patients

There are several reports concerning an impairment of cellular immune response in patients affected by malignant disease. The aim of this study was to evaluate the in vitro effect of Pidotimod, a synthetic biological response modifier, on some immune functions in 14 cancer patients. In particular, we showed that these subjects had a significantly reduced peripheral blood mononuclear cell (PBMC) proliferation both in response to PHA and to Con A in comparison with a group of healthy subjects. Besides, they showed a significantly reduced PBMC IL2 production, which was evaluated both through an ELISA method and a biological assay. The in vitro addition of increasing concentrations of Pidotimod (10, 25 and 50 ug/ml) was able to enhance PBMC proliferation and IL2 production significantly. However, in spite of the addition of Pidotimod, both immune functions in our neoplastic patients did not reach normal values.

Suppression of bovine lymphocyte responses to mitogens following in vivo and in vitro treatment with dexamethasone

Gnotobiotic calves given intramuscular injections of dexamethasone (DM, 0.5 mg kg-1 day-1) showed marked changes in haematological parameters including a neutrophilia and a lymphopaenia. Not only was there a reduction in the numbers of circulating mononuclear cells, but there was also a significant (P less than 0.01) decrease in the in vitro responsiveness of the remaining circulating peripheral blood lymphocytes to the mitogens, phytohaemagglutinin (PHA), concanavalin A (ConA) and pokeweed mitogen (PWM). Responses to all three mitogens were suppressed to a similar degree. Analysis of the circulating mononuclear cell sub-populations before and during DM treatment demonstrated a selective depletion of B cells; the T lymphocyte sub-population that expresses the gamma/delta form of T cell receptor, are CD2-, CD5+, CD8-, CD4- and constitute a major population in peripheral blood of calves. In vitro studies in gnotobiotic and conventional calves confirmed that DM was highly inhibitory for PHA responses but, in contrast to the in vivo findings, showed little effect of DM on ConA responses. Expression of surface antigens after 72 h in vitro culture in the presence of DM were little affected with the exception of BoCD8 and MHC II, which showed increased and decreased expression, respectively. These observations would suggest that distinct mechanisms are involved in glucocorticosteroid suppression of the responses to these two mitogens.

The role of accessory molecules in T-helper activation induced by antigen, lectin, or CD3 antibodies

We examined the role of L3T4 and LFA-1 molecules in T-helper-cell activation, under conditions where the physical stability of T helper-accessory cell interactions was not an issue. T-helper hybridomas were activated by accessory cells coated either with concanavalin A (Con A) or with CD3 antibodies. Activation of the T helper cells was measured by microtubule-organizing center (MTOC) reorientation as an early activation event, and by interleukin-2 (IL-2) production as an indication of a fully matured response. Both parameters were strongly blocked by L3T4 and LFA-1 antibodies in the case of Con A activation. In the case of stimulation with accessory cell-bound CD3 antibody, activation was blocked by LFA-1 but not L3T4 antibody. These results support the notion that L3T4 and LFA-1 molecules play more than a simple adhesion role in T-cell activation. The differential effect of L3T4 antibody in the case of Con A activation vs CD3 activation is consistent with the possibility that L3T4 and the alpha/beta portions of the T-cell receptor must interact during antigen- and lectin-stimulated T-cell activation.