Bovine luteal cells elicit major histocompatibility complex class II-dependent T-cell proliferation

Major histocompatibility complex (MHC) class II molecules are expressed in the bovine corpus luteum (CL) in a manner correlating with luteolysis. Whether bovine luteal cells can stimulate T-cell proliferation in a class II-restricted manner was investigated. Staphylococcal enterotoxin B (SEB) enhances T-cell proliferation by a mechanism requiring MHC class II molecules and was used to examine stimulation of T-cell proliferation by luteal cells. Luteal cells from midcycle or regressing CL (induced by prostaglandin F2 alpha) were cocultured with autologous T cells in the presence of no treatment, SEB (1 microgram/ml), or SEB + anti-MHC class II antibody (3 micrograms/ml); and proliferation was assessed by incorporation of tritiated thymidine. T cells proliferated in the presence of cells from regressing CL more than when in the presence of midcycle cells (118,309 +/- 20,567 vs. 75,261 +/- 12,494 cpm; p < 0.05). Anti-MHC attenuated this response of cells from regressing CL (81,108 cpm +/- 13,249; p < 0.05). Without SEB, T cells proliferated when cultured with cells from regressing, but not midcycle, CL (4637 +/- 816 vs. 2117 +/- 589 cpm; p < 0.03). These results suggest that luteal cells can function as antigen-presenting cells in vitro and that prostaglandin F2 alpha may enhance their ability to present antigen.