Decreased Treg cell frequency in CD40L-, AID-deficient, and XLA patients. Treg cell frequencies among peripheral CD4+ T cells were assessed by analyzing the proportion of CD25+Foxp3+ cells. Dot plots representative for a healthy control and CD40L-, AID-deficient, and XLA patients are displayed in (A). (B) Treg cell frequencies from all patients were significantly lower than those in healthy controls (P < 0.0001 for CD40L-, AID-deficient, and XLA patients).