Activation of NK1.1+T Cellsin Vitroand Their Possible Role in Age-Associated Changes in Inducible IL-4 Production

Abstract

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 activationin vivo.We demonstrate here that NK1.1+T cells can be directly induced to produce IL-4in vitrowhen 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 cellsin 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 NK1.1+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 (CD44high, CD45RBlow, NK1.1−) T cells from aged donors produced IL-4 following polyclonal T cell activation.