New Method for the Expansion of Highly Purified Human Regulatory Granzyme B-Expressing B Cells

Granzyme B (GZMB)-expressing B cells inhibit CD4(+) T-lymphocyte proliferation in a contact- and GZMB-dependent manner, through degradation of TCR zeta or induction of T-cell apoptosis. This regulatory B-cell population is present in human healthy individuals and represents about 1% of circulating B cells. Their small proportion requires the development of expansion methods to enable their study and envision clinical applications. We describe here how to expand GZMB-expressing B cells to obtain more than 90% of highly purified GZMB(+) B cells, and the protocol of B/Tcells coculture for the evaluation of the suppressive function of the GZMB(+) B-cell population.