A persistent T cell expansion in the peripheral blood of a normal adult male: a new clinical entity?

Abstract

SUMMARY A dramatic and persistent T cell expansion in a healthy adult male was initially identified, using anti-T cell receptor for antigen (TCR)-specific MoAbs. The expanded T cells were found to be expressing TCR containing Vα 12.1 and V β 5.2, and they composed approximately one third of all the CD8+ T cells. The cells were shown to be not only non-activated (HLA-DR−, IL-2R−) but also of ‘virgin’ cell type (CD45RA+/CD45RO−) and they persisted over the observation period of more than one and a half years. Various T and B cell markers, and all other laboratory and physical parameters analysed, were normal. The expanded CD8+ T cells were further characterized by polymerase chain reaction (PCR) amplification, using Vβ- and Cβ-specific primers, followed by hybridization with Jβ-specific probes. Close to 90% of the Vα 12.1+ Vβ 5.2+ T cells were found to utilize the Jβ 2.5 gene segment, thus strongly suggesting the expanded T cells to be monoclonal. The condition may constitute a T cell counterpart to ‘monoclonal gammopathy of undetermined significance’ (MGUS), and by analogy we suggest it should be designated ‘monoclonal T cell expansion of undetermined significance’ (MTUS).