The CD4+ lymphocytes of RA patients are already known to exhibit certain features similar to those observed for these cells in the healthy elderly, including relatively short telomeres, decreased amount of surface CD28, decreased overall proliferation etc. To investigate the possibility of accelerated aging of CD4+ lymphocytes of RA and AD patients, a new flow-cytometric technique of studying lymphocyte proliferation has been utilised. This evidence concerns the gene CD28 and rheumatoid arthritis.