CD4 and agammaglobulinemia: To evaluate the diagnostic accuracy of peripheral T and B cell subsets in discriminating primary from secondary hypogammaglobulinemia, values for each of the significantly changed parameters (i.e., the proportions of memory CD4+ T cells, CD4+ T follicular cells, naïve B cells, memory/marginal zone B cells, class-switched memory B cells, transitional B cells, IgM+/- plasma cells and CD21low B cells) were ranked, fitted into logistic regression and plotted into receiver operating characteristic (ROC) curves (Figure S5).