Regulation of immune functions by human surfactant.

Human peripheral blood mononuclear cells (MNC) were incubated in vitro with highly purified human surfactant to examine its effect on various T cell functions. Surfactant inhibited DNA synthesis by lymphocytes in response to concanavalin A (Con A), phytohemagglutinin (PHA), and in the autologous mixed lymphocyte reaction (AMLR). In contrast, surfactant had no effect on pokeweed-mitogen (PWM, T cell-dependent B lymphocyte mitogen)-induced DNA synthesis or on interleukin-2 (IL-2) receptor expression on T cells activated with PHA, Con A or PWM. Furthermore, surfactant had either no effect or enhanced (depending upon the concentration of IL-2 used) the response of exogenous recombinant IL-2 on IL-2-dependent T cell line, In vitro addition of recombinant IL-2 corrected the suppressive effect of surfactant on the AMLR. These data show immunosuppressive effect of surfactant on T lymphocyte functions.