CD4 and autoimmune disease: Although phenotypic and functional analysis of CD4+CD25−Foxp3+ T cells in autoimmune diseases such as systemic lupus erythematosus (SLE) and primary Sjögren‘s syndrome have been performed (18–23), there is still considerable controversy as to their function: Bonelli et al. proposed that increasing proportions of CD4+CD25−Foxp3+ T cells functionally resemble regulatory T cells in patients with SLE (22), whereas Yang et al. concluded that most CD4+CD25−Foxp3+ T cells are likely previously activated conventional T cells (23).