CD4 and systemic lupus erythematosus: Moreover, both lipocalin-2 (LCN2) expression in CD4+ T cells from LN patients, LCN2 expression in peripheral blood mononuclear cells (PBMCs), and splenic CD4+ T cells from MRL/lpr mice were higher than those in controls, correlating with SLE disease activity index and urine protein and serum creatinine expression (15).