T-cell expansions in patients with multiple myeloma have a phenotype of cytotoxic T cells

The presence of T-cell clones in peripheral blood has been previously shown to be associated with a survival advantage in patients with multiple myelo ma and suggests that the expanded T-cell populations may be involved in an anti-tumour response. We studied the T-cell receptor (TCR) repertoire of 38 patients with myeloma to identify and characterize the expanded T-cell pop ulations by now cytometry. T-cell expansions were found in 79% of the patie nts. The expansions occurred randomly among the 21 variable regions of the TCR beta chain (V beta) studied, representing 62% of the V-beta repertoire, and were stable during an 18-month follow-up. The phenotype of the expande d V-beta populations was predominantly CD8(+), UD57(+), CD28(-) and perfori n(+), which differed significantly from the other nonexpanded V beta popula tions. The expression of the apoptosis markers Fas (CD95) and bcl-2 were si milar between the expanded and non-expanded V beta populations. In conclusi on, expanded T-cell populations were frequent in patients with myeloma, the y remained unchanged during follow-up and had phenotypic characteristics of cytotoxic T cells. These data add further support to the concept that the T-cell expansions may have an immunoregulatory role in myeloma.