CD27 and Hermansky-Pudlak syndrome: Studies using peripheral blood samples from HPS patients have shown that levels of CD38 + memory CD27-B cells, IgA + memory CD27+ B-cells, IgM+ and IgD + B cells, and CD39 + T helper cells were increased, and that CD39-T helper cells was reduced in HPS-PF when compared with unaffected controls (El-Chemaly et al., 2018a).