CD19 and systemic sclerosis: To investigate the distribution of memory B cell subsets in the peripheral blood of SSc patients and HCs the frequencies of CD19+IgD−CD27−CD38+ double negative (DN) 1, CD19+IgDloCD27+CD38+ unswitched, CD19+IgD−CD27+CD38+CD95− resting switched and CD19+IgD−CD27+CD38−CD95+ activated switched memory (ASM) B cells were determined (Figure 1A) in highly enriched B cells (Figure 1B).