Atypical T cells are the progeny of naive T cells.

CD4⁺ T cells were isolated by negative selection, and cell surface staining was performed for CD45RB, CD45RA, CD45RO, and CD62L. Cells were sorted according to their expression of CD45RO and then of CD45RB, CD45RA, and CD62L. DNA was extracted from the subsets illustrated, and TREC content was measured by real-time PCR. Results from 3 healthy controls (22, 33, and 57 years old) and from 3 patients with early RA (45, 61, and 62 years old) were pooled. Values are normalized to the naive cell TREC content of each person. Subsets dominant in healthy controls are shown by solid bars, and atypical subsets dominant in RA patients are shown by hatched bars. Results represent the mean and SD of 3 independent experiments.