CD27 and systemic lupus erythematosus: As has been described in extensive research conducted by our and other research teams, a shift of B cell population to advanced differentiated compartments, namely reduction of naïve (IgD+CD27−) and non-switched memory (IgD+CD27+) and increase in the proportion of switched memory (IgD-CD27+) and double negative (DN) (IgD-CD27−) B cells, is evident in SLE patients [122,123,124,125,126,127].