Consistently, stimulated PBMCs from healthy females and males with Klinefelter syndrome, men with XXY karyotype, showed higher CD40L expression level in T cells and higher number of Cluster of differentiation 3 (CD3)+ CD40L+ T cells compared with healthy males and women with Turner syndrome, women with X karyotype (Sarmiento et al. 2019). The gene discussed is CD40LG; the disease is Klinefelter syndrome.