Mutations in STAT3 compromise the generation of CD4⁺ memory and CXCR5⁺CD45RA⁻ Tfh cells. (A-B) The frequency of naive (CD45RA⁺CCR7⁺), memory (CD45RA⁺CCR7^−/+), and CXCR5⁺CD45RA⁻ CD4⁺ T cells in PBMCs was determined for healthy donors and STAT3_MUT patients. (A-B) Representative dot plots from 1 donor and 1 patient. (C-F) The frequency of (C) total CD4⁺ T cells, (D) naive (CD45RA⁺CCR7⁺), (E) memory (CD45RA⁺CCR7^−/+), and (F) CXCR5⁺CD45RA⁻ CD4⁺ T cells from all healthy donors (total CD4⁺ T cells, n = 54; naive CD4⁺ T cells, n = 70; memory CD4⁺ T cells, n = 70; CXCR5⁺CD45RA⁻ CD4⁺ T cells, n = 61) and STAT3_MUT patients (n = 14) was examined.