THE UMBILICAL-CORD BLOOD ALPHA-BETA-T-CELL REPERTOIRE - CHARACTERISTICS OF A POLYCLONAL AND NAIVE BUT COMPLETELY FORMED REPERTOIRE

Umbilical cord blood (CB) constitutes a promising alternative to bone marrow for allogeneic transplantation and is increasingly used because of the reduced severity of graft-versus-host disease after CB transpl antation. We have compared the T-cell receptor beta chain (TCRB) diver sity of CB lymphocytes with that of adult lymphocytes by analyzing the complementarity determining region 3 (CDR3) size heterogeneity. In ma rked contrast to adult samples, we observed bell-shaped profiles in al l of the 22 functional beta-chain variable (BV) subfamilies that refle ct the lack of prior antigenic stimulation in CB samples. However, the mean CDR3 size and BV usage were comparable between CB and adult samp les, BJ2 (65%) segments were used preferentially to BJ1 (35%), especia lly BJ2S7, BJ2S5, BJ2S3, and BJ2S1, in both CB and in adult lymphocyte s, We therefore conclude that although naive as reflected by the heter ogeneity of the CDR3 size, the TCRBV repertoire appears fully constitu ted at birth. The ability to expand TCRB subfamilies was confirmed by stimulation with staphylococcal superantigens toxic shock syndrome tox in-l and staphylococcal enterotoxin A, This study provides the basis f or future analysis of the T-cell repertoire reconstitution following u mbilical CB transplantation. (C) 1998 by The American Society of Hemat ology.