Antigen presentation is inhibited in vivo by betamethasone

Aim of the present study was to assess whether betamethasone, a synthetic glucocorticoid used as immunosuppressant, could modify in vivo the antigen presentation by antigen presenting cells (APC). Interleukin-2 (IL-2) production by a T cell hybridoma specific for the hen egg white lysozyme (HEL) cultured in the presence of HEL and APC from treated or control mice was utilized as read out. Betamethasone induced a dose-dependent inhibition of antigen presentation. Fifty percent maximal response was observed with 1152 (95% confidence interval: 948-1419) resident peritoneal macrophages from untreated animals, and 5843 (4700-7445, 21, 235 (12,857-43,705), 28,313 (20,847-40,955) macrophages from mice injected for 3 days with betamethasone 10, 25, and 50 mg/kg respectively. Similar findings were obtained with spleen cells. When given for 3 days at 25 mg/kg, betamethasone reduced the number of cells recovered from the peritoneum by approximately half and from the spleen by one order of magnitude. One day vs. 3 days treatment resulted in similar recovery of cells but lower inhibition of APC function. In the experimental conditions utilized, no carryover of betamethasone with APC could be demonstrated and no reversal of inhibition was observed by increasing the antigen concentration. The data here presented demonstrate that short curses of high dose betamethasone specifically impair antigen presentation. Thus, this mechanism appears to be involved in the immunosuppressant activity of betamethasone.