In the control group, serum levels of IFNα were associated with the expression of CD25 in CD4+CD28null, whereas lupus patients with high IFN-score (IFNpos) exhibit an increased proportion of activated CD25+CD28null cells, with no differences in the total CD4+CD28null subset compared to the rest of patients. Here, CD4 is linked to systemic lupus erythematosus.