In an ex vivo study assessing CD38 expression on various immune cells within peripheral blood mononuclear cells (PBMCs) from SLE patients, plasma cells and plasmablasts were noted to have the highest levels of CD38 expression, succeeded by natural killer (NK) cells, pDCs, a subset of regulatory T cells, and naive T cells [182]. Here, CD38 is linked to systemic lupus erythematosus.