PIP3 levels in stimulated T cells positively correlated with the frequency of CD4+ T cells and negatively correlated with the frequencies of CD8+, EMRA CD4+, and EMRA CD8+ T cells.<h4>Conclusions</h4>We describe the range of variation of PI3Kδ activity in T cells from a large cohort of patients with SLE and from healthy subjects. Here, CD4 is linked to systemic lupus erythematosus.