TREC content of CD4⁺ T cells is decreased in RA patients.

(A) TREC content of total CD4⁺ T cells is decreased in RA patients. CD4⁺ T cells were negatively selected using magnetic beads, and DNA was extracted from the enriched population. TREC content was measured by real-time PCR. Controls (♦) are compared with RA patients (⋄, early RA; ▵, resistant RA). CD4⁺T-cell TREC content in RA patients was lower than in healthy controls (P < .0001). TREC content decreased with age in both groups (controls, r = −0.816, P < .0001; RA, r = −0.229, P = .132). (B) TREC content of naive CD4⁺ T cells is lower in RA patients. Naive CD4⁺ T cells were sorted by flow cytometry (on the basis of their CD45RB^bright, CD45RA⁺, CD62L⁺ phenotype) from total CD4⁺ T cells. TREC content was measured as above. Controls (♦) are compared with RA patients (⋄, early RA; ▵, resistant RA). In contrast to total TREC values, there was no significant relationship between the TREC content of naive T cells and age. TREC content of naive T cells in RA patients remained significantly different from that in controls (P < .0001). TREC content was lower in early and resistant RA groups than in controls (controls vs early patients,P = .014; controls vs resistant patients,P < .0001). There was also a significant difference in TREC content between patients with early and resistant RA (P = .005).