Flow cytometric identification of human CD3+CD4+T- and CD19+B-cell subsets for correlation with absolute TREC and KREC quantity post alloHSCT. (A) Human peripheral blood CD3+CD4+ T-cell subsets were defined as CD45RA+CCR7+CD62L+CD27+CD31+ naïve T cells, CD45RA+CCR7+CD62L+CD27+CD31- naïve T cells and CD45RO+ memory T cell cells. (B) Within the CD19+ B cell compartment, B-cell subsets were identified by gating on IgD+CD27-CD38hi transitional B cells, IgD+CD27-CD38int naïve B cells and CD27+ memory B cells. Dotplots in A and B are representative of a patient at day 90 post alloHSCT. Numbers indicate percentages of gated cell subsets. (C) Absolute TREC, KREC and TRAC copy numbers were extrapolated from standard regression lines obtained by the determination of Ct values for the serial diluted triple insert plasmid encoding one copy of TREC, KREC and TRAC. Shown is one representative standard line for each gene. m indicates the slope of the linear regression line and r2 the correlation between linear regression line and obtained Ct-values as a marker for the accuracy of the respective standard dilutions.