CD40LG and Decreased total leukocyte count: Her father (I:1) had mild leukopenia, and while his lymphocyte subset analysis did not include NK cells (Table 1), his B cells were decreased, as were IgG and IgA class-switched memory B cells and immature/transitional B cells, but levels of IgG, IgM, and IgA were normal (Table 1 and Supplemental Table 1).