Influence of sex hormones on Coxsackie B-3 virus infection in Balb/c mice

Background and “spontaneous” proliferation are terms often used for the proliferative activity normally exhibited by peripheral blood mononuclear cells (MNC) in vitro. In this report, we show that Interleukin-2 (IL-2) added to unfractionated MNC but not to isolated T or non-T cells significantly increased their proliferative activity. The cells responding to IL-2 stimulation from MNC were OKT3 positive lymphocytes. In addition, treatment of MNC with either a monoclonal anti-HLA-DR antibody (in the absence of C′) or Cyclosporin-A strongly suppressed the “background” whereas treatment of MNC with the 3A1 monoclonal anti-human T cell antibody did not modify “spontaneous” proliferation of these cells. IL-2 could not restore or increase the proliferative activity of MNC exposed to the anti-HLA-DR antibody or Cyclosporin-A while the T cell growth factor significantly enhanced proliferation of MNC cultured in the presence of the OKT4 antibody. Taken together these results strongly suggest that IL-2 responding T cells from MNC become sensitive to IL-2 by interacting with HLA-DR antigens on B lymphocytes and/or monocytes contained in MNC (resting T cells are Dr^?). By a similar mechanism we have previously shown that T cells acquire responsiveness to IL-2 in the autologous mixed lymphocyte reaction (AMLR). Since all the cells that participate in AMLR are present in MNC, we postulate that a “mini” AMLR taking place within MNC may explain the “spontaneous” proliferation of peripheral blood mononuclear cells.