Interleukin-2 and Serum Thymic Factor Enable Autologous Rosette-forming T Lymphocytes to Generate Helper and Cytotoxic Functions

Abstract

The autologous rosette-forming human T cells (Tar cells) isolated by means of their ability to form rosettes with autologous erythrocytes were characterized by the use of OKT monoclonal anti-human T cell subset antibodies and a monoclonal anti-HLA-DR antibody. The phenotype of Tar cells was OKT 3+4+8+DR- as determined by both indirect immunofluorescence microscopy and complement-mediated killing of 51Cr-labeled Tar cells. Tar lymphocytes were able to develop cytotoxicity against allogeneic and trinitrophenol (TNP)-conjugated autologous target cells in the presence of interleukin-2 (IL-2) or serum thymic factor. These cells showed little or no cytotoxicity in the absence of IL-2 or serum thymic factor. Tar lymphocytes generated helper function for B lymphocytes in the presence of IL-2 in both pokeweed mitogen (PWM) and purified protein derivative (PPD)-stimulated cultures. Non-IL-2-treated Tar cells did not exhibit any helper activity on B cells. Pretreatment of Tar cells with 1000-1500 rad of X ray made these cells unable to develop helper function for B lymphocytes. It is concluded that: OKT 3+4+8+Dr- Tar cells are able to generate cytotoxicity against alloantigens and TNP-labeled self structures provided they are stimulated by IL-2 or serum thymic factor; these cells need both to proliferate and to receive help from IL-2 to develop helper cells capable of assisting B lymphocyte differentiation into plasma cells in both PWM- and PPD-stimulated cultures.