Despite increased frequencies of CD4+CD28null T cells in the circulation of RA patients, however, their contribution to erosive disease is still unclear: while studies from Pawlik and colleagues and Goronzy and colleagues found associations between circulating CD4+CD28null T cells and erosive disease [4,10], Martens and colleagues and Gerli and colleagues did not observe such associations [3,9]. Here, CD4 is linked to rheumatoid arthritis.