CD27 and myeloid sarcoma: When testing purified B cell subsets, however, CD27+IgD- class-switched memory B cells (CSM) from MS patients displayed more pronounced chemotactic activity than those from control donors [HC: 2.89 ± 0.31 (chemotactic index, CI); MS, relapse: 3.30 ± 0.28; MS, remission: 2.55 ± 0.30; p < 0.05 each] (Figure 4B), while trafficking of CD27-IgD+ naïve B-cell subtypes across HIBCPP was unequivocally very low in both cohorts.