Efficient short-term expansion of human peripheral blood regulatory T cells for co-culture suppression assay

Regulatory T cells (Tregs) are a small population of CD4+ lymphocytes and play a key role as suppressors of the immune system, a role that can be identified by employing a co-culture suppression assay. Conventional protocol requires a long period of in vitro expansion of Treg numbers; hence, this study describes an establishment of a co-culture suppression assay using a short-term expansion of peripheral blood (PB) Tregs and autologous T cells (Tconvs) IL-2-pre-cultured in parallel for the same length of time, thereby obviating the need of freeze/thawed autologous Tconvs. Tregs and Tconvs were isolated from PB mononuclear cells employing magnetic bead-aided depletion of CD8+ cells followed by cell sorting of CD4+ CD25high+CD127low- (Treg) and CD4+ CD25-CD127+ (Tconv) cell populations. Following a 3-day co-cultivation period under optimized conditions, Treg suppression activity was monitored by comparing using flow cytometry the number of carboxyfluorescein succinimidyl ester-labeled Tconvs to that of Treg-minus control. The assay allowed significant differentiation between Treg suppression activity of patients with active rheumatoid arthritis and those in remission. This method should be more convenient and time-saving than the conventional Treg suppression assay in current use.