CD19 and lymphopenia: When compared to HCs, KTRs presented global lymphopenia (median: KTRs = 1,256 vs. HCs = 1,996/mm3; P = 0.0455; S3A Fig), involving mainly B cells (median CD19+: KTRs = 45 vs. HCs = 213/mm3, P = 0.0002; S3C Fig) and CD4+ T cells (median CD4+: KTRs = 484 vs. HCs = 1,007/mm3; P = 0.0007; S3E Fig).