Thymic function is associated with peripheral naive CD4⁺ T-cell counts. Naive T-cell (CD45RA⁺, CD27⁺) counts were quantified in CD4⁺ (left) and CD8⁺ (right) peripheral T cells from HIV-1 infected patients (n = 29). (A) Correlation between naive T-cell counts and thymic function as defined by the sj/βTREC ratio. (B) Correlation between naive T-cell counts and the percentage of cycling cells in CD4⁺ or CD8⁺ naive T-cell compartments.