Disulfide-linked GARP/TGF-β1 complexes are released by stimulated human Tregs, which naturally express GARP.
The indicated Treg and Th cell populations were left resting or stimulated with anti-CD3/CD28 antibodies in serum-free medium. A. Supernatants were collected after 48 hours. B. Cell lysates were collected after 24 hours and IP with an anti-GARP antibody. Supernatants (A) and immunoprecipitated lysates (B) were submitted to SDS-PAGE under non-reducing conditions, then analyzed by WB with anti-LAP antibodies. Similar results were obtained with freshly isolated CD4+ T cells from 2 other donors and with expanded CD4+ T cells from 5 others donors.