In MRL/lpr mice, a murine model of SLE characterized by the accumulation of CD4+CD25+Foxp3+ Treg cells in lymphoid organs [88], the onset of the autoimmune disease correlates with a reduced functional capacity of Treg cells that show a distinct phenotype (i.e., increased CD69 and reduced CD62L expression). Here, CD4 is linked to systemic lupus erythematosus.