Human bone marrow contains significant numbers of IgA⁺ plasma cells. (A) Proportions of bone marrow plasma cells expressing icIgG, icIgA, or icIgM. Bone marrow plasma cells and their isotype were assessed cytometrically as depicted in Figure S2. (B) Expression of CXCR4, CCR10, and CCR9 by CD38^high bone marrow plasma cells was analyzed (open histograms and black MFI values) and compared with control stainings (gray histograms and MFI values).