Increased numbers of CD5+ B cells and T cell receptor (TCR) γδ+ T cells are associated with younger age of onset in rheumatoid arthritis (RA)

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Abstract
Patients presenting with RA before the age of 45 years (younger onset) are known to have more aggressive disease compared with patients presenting after the age of 65 years (older onset). Coordinated expansion of circulating CD5+ B cell and TCR γδ+ T cell levels has been reported in patients with RA. This study assesses the peripheral blood levels of these two cell types in RA patients with younger and older onset of disease. CD5+ B cell levels were significantly elevated in the younger onset RA group (26±6 γδ+4±5%) compared with the older onset RA group (14±2 γδ+1±2%; P+ T cell levels were also significantly raised in the young patients (4±0 γδ+0±9%) compared with elderly patients (1±6 γδ+0±2%; P+) were similar in both groups (young 66±4 γδ+3±3%; old 74±3 γδ+3±4% (mean γδ+s.e.m.); NS). Total B cell levels (CD19+) were also similar in these groups (7±7 γδ+0±7%versus 8±9 γδ+1±8%; NS). A significant positive correlation was observed between the CD5+ B and TCR γδ+ T cell types in the patients (r= 0±72, P+ B cell and TCR γδ+ T cell levels to the elderly controls (CD5+ B cells 30±2 γδ+3±0%; TCR γδ+ T cells 3±0 γδ+0±8%). Conversely, older onset RA patients had CD5+ B cell levels similar to the young controls (12±3 γδ+1±9%). Spontaneous in vitro synthesis of immunoglobulins (IgM, IgA and IgG) and rheumatoid factors (IgM and IgA isotypes) were not significantly different in both patient groups. The coordinate expansion of circulating CD5+ B cells and γδ+ T cells seen in patients with RA presenting before 45 years of age and not after 65 years of age may suggest a potential role for these cells in more aggressive disease states.