While evidence suggests that deficiency in a certain subset of T cells with regulatory properties (Treg) is associated with preeclampsia (Cerdeira et al., 2012; Przybyl et al., 2015) our expanding knowledge of the complexity of these T cell subsets is likely to reveal associations between this disease and several members of the CD4 family of T cells (Ahn et al., 2020; Saigusa et al., 2020; Deer et al., 2021). The gene discussed is CD4; the disease is preeclampsia.