Longitudinal analysis of T cells responding to tetanus toroid in healthy subjects as well as in pediatric patients after bone marrow transplantation:the identification of identical TCR-CDR3 regions in time suggests long-term stability of at least part of the antigen-specific TCR repertoire

To understand the nature of long-term Th immune responses, we investigated in the present study the TCRBV gene repertoire of CD4(+) T cells specific f or the recall antigen tetanus toroid (TT) in recipients of an allogeneic bo ne marrow transplantation (allo-BMT) at several time points after transplan tation and in their BM donors. We observed that the TCR repertoire of TT-sp ecific CD4(+) Th cells was heterogeneous, and differed between allo-BMT rec ipients and their respective donors. Some individuals, however, used simila r TCR-complementarity-determining region (CDR)3 motifs that could reflect r ecognition of and selection by similar promiscuous epitopes of TT. Longitud inal analysis of this TT-specific T cell response revealed that T cells wit h completely identical TCR were present at several time points after the fi rst analysis in allo-BMT recipients, most probably reflecting long-term sta bility of at least part of the antigen-specific TCR repertoire. Similar sta bility of the TT-specific TCR repertoire in time was also noted in the allo -BMT donors. These observations reveal that within a given individual the d ominant antigen-specific T cell clones persist in time in an otherwise dive rse TT-specific CD4(+) T cell immune response.