The relationship between TRECs and the percentage of circulating CD4⁺ CD45RA⁺ T lymphocytes.

TRECs per 10⁶ PBMCs were measured and plotted (y-axis) for samples that had greater or less than 1% circulating CD4⁺CD45RA⁺ lymphocytes (≤ 1%, ▪, solid line versus > 1%, ○, dashed line), as a function of time from transplantation (x-axis). The difference between the 2 curves is significant atP < .01. Differences in the proportion of T cells expressing the naive, CD4⁺ CD45RA⁺ surface phenotype, however, could not account for 55% of the variation in measured TRECs (r² derived from nonparametric regression model by using same data depicted). Note that the lower limit of detection for TRECs was 100 TRECs/10⁶ PBMCs in the assay used.