Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Immune deviation of cytolytic T cell function, induced by type 2 cytokines like IL-4, is an attractive concept to explain failure of the immune system in some diseases. However, this concept is challenged by previous conflicting results on whether type 2 cytokine-producing CD8+ T cells are cytolytic. Therefore, we have analyzed the relationship between cytolytic activity and cytokine production among large numbers of primary CD8+ T cell clones. Single murine CD8+ T cells of naive phenotype were activated at high efficiency with immobilized Abs to CD3, CD8, and CD11a in the presence of IL-2 (neutral conditions) or IL-2, IL-4, and anti-IFN-γ Ab (type 2-polarizing conditions) for 8–9 days. Under neutral conditions, most clones produced IFN-γ without IL-4 and were cytolytic. Under type 2-polarizing conditions, most clones produced IFN-γ and IL-4 but displayed variable cytolytic activity and CD8 expression. Separation on the basis of surface CD8 levels revealed that, compared with CD8high cells from the same cultures, CD8low cells were poorly cytolytic and expressed low levels of perforin mRNA and protein and granzyme A, B, and C mRNA. A similar, smaller population of noncytolytic CD8low cells was identified among CD8+ T cells activated in mixed lymphocyte reaction with IL-4. Variable efficiency of generation of the noncytolytic cells may account for the differing results of earlier studies. We conclude that IL-4 promotes the development of a noncytolytic CD8low T cell phenotype that might be important in tumor- or pathogen-induced immune deviation.</jats:p>