Examination of differentiation, proliferation and distribution of lymphoid cells in mice by immunohistochemical analysis post in vivo administration of recombinant interleukin-II.

Augmentation of lymphoid cell activity has been observed after administration of a variety of biological response modifiers (BRM) in both preclinical and clinical studies. Little is known of in vivo control of the proliferation and early differentiation of lymphoid cells after administration of a BRM in lymphoid tissues. In view of the role that lymphoid activity plays in resistance of the host to disease and the recent demonstration that Interleukin II (IL-2) has a profound effect on regulation of immune function both in vitro by activation of cytolytic cells and in vivo by augmenting lymphoid cell activity, studies to evaluate possible morphological changes in differentiation, proliferation and distribution in lymphoid organs after in vivo administration of IL-2 were performed in conjunction with evaluation of cellular immune response modification using a functional cytolytic assay. Our findings indicate increased activation of cytolysis by spleen cells with no observed apparent corresponding changes in lymphoid morphology in either lymph node, thymus, or splenic organs. In contrast to this, marked thymic medullary proliferation was observed in animals receiving 100,000 units of IL-2, i.p., 1 thru 5 days. No thymic changes were observed after only a single i.p. injection of IL-2. Augmentation of cytolytic activity by thymic cells was not observed.