Challenge of DCs with alloreactive, but not with nonspecific T lymphocytes, results in secretion of processed, bioactive IL-1β.

(A, B) DCs, untreated (lanes 1 to 3) or treated with LPS for the last 40 hours (lanes 4 to 6) were challenged with activated allospecific T lymphocytes (allo T, lanes 2 and 5) or autologous activated T lymphocytes (auto T, lanes 3 and 6) at a T-cell:DC ratio of 10:1. Cell lysates (panel A) and supernatants (sups, panel B) were analyzed as for their content in pro–IL-1β or IL-1β by Western blot. (C) Bioactivity of secreted IL-1β: 100 μL aliquots of supernatants from the different culture conditions was added to HUVEC and incubated at 37°C for 20 hours. At the end of the incubation, the ICAM1 molecules expressed by HUVEC were quantified by ELISA.