Interleukin-10 inhibits apoptotic cell death in infectious mononucleosis T cells

Cytokine production in the immune response to murine gammaherpesvirus 68

Cytokine profiles were determined following intranasal infection of C57BL/6J mice with murine gammaherpesvirus 68 (MHV-68). Spleen, mediastinal, and cervical lymph node cells from infected mice produced high levels of interleukin 6 (IL-6) and gamma interferon (IFN-gamma) and lower levels of IL-2 and IL-10 following in vitro restimulation. Little or no IL-4 or IL-5 was detected. Cytokine production was generally maximal at 10 days after infection, correlating with viral clearance from the lung, although significant levels were seen as early as 3 days after administration of the virus. In vitro infection of naive splenocytes induced B-cell- dependent secretion of IL-6 and IL-10, whereas IFN-gamma and IL-2 were produced only by cells that had been primed in vivo. Depletion of B lymphocytes from primed splenocyte populations did not, however, abrogate IL-6 and IL-10 production. Highly purified immune T cells made IL-6, IL-10. and IFN-gamma following in vitro restimulation with MHV-68. Thus, IL-6 and IL-10 are components of both the acquired and the innate host response. These cytokines have potential roles in the establishment and maintenance of persistent infection.

Characterization of apoptosis-resistant antigen-specific T cells in vivo

Clonal deletion via activation-induced apoptosis (AIA) of antigen-specific T cells (ASTC) plays a very important role in the induction of peripheral tolerance. However, none of the studies performed so far has shown a complete deletion of ASTC, a small population always persisting in the periphery. The mechanism by which this small population of ASTC escapes AIA has not been determined. Since the existence of these ASTC may influence the outcome of autoimmune diseases and long-term graft survival, we have characterized the properties of these residual ASTC in vivo with the objective of determining mechanisms that may contribute to their persistence. It was found that the resistance of the residual ASTC to AIA is not due to lack of activation or Fas/Fas-L expression. Compared to those susceptible to AIA, the residual ASTC express a high level of Th2-type cytokines that may help them to escape from AIA. Furthermore, they are able to suppress proliferation of other ASTC, suggesting they may, in fact, prolong tolerance in vivo.

Altered IL-10 levels in trauma patients' M phi and T lymphocytes

Trauma results in concomitant immunosuppression and elevated monocyte (M phi) inflammatory cytokine levels. The augmenting or ameliorating effect of IL-10 in septic complications after trauma is controversial. Here, IL-10 levels of trauma patients' and normals' PBMC, isolated M phi, and isolated T cells were assessed and correlated to their PBMC mitogen responses, their T-cell proliferation in an APC independent system, and their M phi production of elevated TNF-alpha levels. Trauma patients with depressed PBMC responses to PHA stimulation also had significantly decreased IL-10 levels in their stimulated PBMC supernates (P = 0.0022) and their MDP-stimulated isolated M phi population (P = 0.0004). However, patients with depressed PHA responses could have either normal or depressed T-cell proliferation in an anti-CD3-, anti-CD4-stimulated system. If APC-independent T-cell proliferation was depressed, induced IL-10 levels were suppressed (P = 0.007). However, if APC-independent T-cell proliferation was normal or elevated, IL-10 levels could be normal or elevated (P = 0.018). Decreased IL-10 levels correlated with depressed mitogen responses and depressed T-cell proliferation. IL-10, therefore, could not be inducing trauma patients' immunosuppression. Patients with elevated M phi TNF-alpha levels had depressed M phi IL-10 levels.