CD4 and systemic lupus erythematosus: On the other hand, it has recently been shown, that an increased histone H3 lysine 27 trimethylation enrichment at the hematopoietic progenitor kinase 1 (HPK1) promoter of SLE CD4+ T cells (relative to controls) inhibits the HPK1 expression and contributes to autoimmunity in SLE [86].