Activation of NK1.1(+) T cells in vitro and their possible role in age-associated changes in inducible IL-4 production

Interleukin (IL)-12 or IL-4 produced early in an immune response directs the differentiation of naive antigen-activated CD4(+) T cells down a Th1 or Th2 pathway. The NK1.1(+) subset of T cells promptly produces IL-4 following activation in vivo. We demonstrate here that NK1.1(+) T cells can be directly induced to produce IL-4 in vitro when activated under serum-free culture conditions. Platelet-derived growth factor in cell culture medium was inhibitory to the production of IL-4 by NK1.1(+) T cells in vitro. Lymphocytes obtained from secondary lymphoid organs of aged mice produced greater quantities of IL-4 following stimulation than lymphocytes from mature adult animals. Aged mice expressed elevated percentages of NR1.1(+) T cells in their secondary lymphoid organs and peripheral blood. While this cell type was responsible for the total early IL-4 produced by lymphocytes from mature adult mice, both NK1.1(+) and memory phenotype (CD44(high), CD45RB(low), NK1.1(-)) T cells from aged donors produced IL-4 following polyclonal T cell activation. (C) 1997 Academic Press.