FIG 1.

Regulated model for Tcrb VDJ rearrangement. In wild-type animals, the ratio of VDJ⁺/DJ to VDJ⁻/VDJ⁺ cells is roughly 60% to 40% for both the Igh and Tcrb loci (25, 44, 45); such a regulated model as depicted here straightforwardly accounts for the actual rearrangement pattern (2). The numbers next to the arrows represent the hypothetical cell numbers that are predicted at the differentiation stage of thymopoiesis to obtain a final 60:40 ratio (2) of VDJ⁺/DJ and VDJ⁻/VDJ⁺ cells that are detected in wild-type thymocytes.