PDCD1 and systemic lupus erythematosus: Notably, a memory CD4+CD152+PD1+ T cell subset (CD4+CD152+PD1+CD45RO+CD25-FoxP3-) was enriched in SLE (median: 2.17%, interquartile range: 1.66 to 7.74% of CD45+ PBMCs) versus control (1.34%, 1.06-1.58%; p = 0.00267).