Immunoregulation in hypersensitivity pneumonitis. I. Differences in T-cell and macrophage suppressor activity in symptomatic and asymptomatic pigeon breeders.

Abstract

Cell-mediated immunity delineates symptomatic from asymptomatic pigeon breeders better than the presence of precipitating antibodies or HLA haptotypes. We therefore investigatedin vitro lymphocyte function in asymptomatic and symptomatic pigeon breeders. Peripheral blood, T, B, and adherent numbers were equal in both groups. Although the response to an optimum dose of concanavalin A was similar in both groups, the asymptomatic group revealed a reduced response to an optimum concentration of phytohemagglutinin and pokeweed mitogen. This decreased mitogen-induced proliferation was abrogated if cells from asymptomatic patients were precultured in medium alone for 48 hr before stimulation. A similar preincubation procedure, however, decreased the response to subsequent mitogenic stimulation in the symptomatic patients. As this suggested the possibility of heightened immunosuppression in the asymptomatic group, suppressor cells were studied. The numbers of FCγ-bearing T cells were similar in both groups and did not differ from control values. In addition, concanavalin A-induced suppressor-cell activity did not differ in either group. Nonetheless, fresh T cells, adherent cells, and peripheral blood mononuclear cells (PBMC) preincubated with pigeon serum decreased the response of preincubated autologous PBMC to mitogens and antigens in asymptomatics. A similar suppression did not occur in autoch-thonous cocultures of PBMC from symptomatic patients. These data suggest that there may be cellular suppressor influences in the asymptomatic group which are absent or nonfunctional in the symptomatic patients. Although this may be useful in distinguishing between the groups, the relationship of these suppressor cells, if any, to the pathogenesis of hypersensitivity pneumonitis awaits further study.