Alterations of T cell repertoire after bone marrow transplantation: characterization of over-represented subsets.

We recently demonstrated that frequencies of T cell receptor-V (TcR-V)-specific subsets are frequently altered after both allogeneic and autologous BMT. The data reported here describe several characteristics of altered T cell subsets: (i) their capacity to endure peripherally, (ii) their correspondence to clonal donor T cell subsets, (iii) the origin of the clone (in one case amenable to analysis) from a mature T cell and not from new lymphopoiesis, and (iv) the presence of such a clone throughout a year of follow-up in a patient with chronic graft-versus-host disease (GVHD) in whom it represented up to 1/10th of CD3+ peripheral blood lymphocytes (PBL) and was found to be host-reactive. Taken together, these findings provide direct evidence for the oligoclonality of a large proportion of the peripheral T cell repertoire in patients subsequent to bone marrow transplantation, possibly accounting for their frequent depressed immune status. Moreover, the anti-host reactivity demonstrated in a clone from the patient with chronic GVHD strongly suggests that an oligoclonal response can be linked to a pathological process.