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 myeloma 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 populations by flow cytometry. T‐cell expansions were found in 79% of the patients. The expansions occurred randomly among the 21 variable regions of the TCR β chain (Vβ) studied, representing 62% of the V‐β repertoire, and were stable during an 18‐month follow‐up. The phenotype of the expanded V‐β populations was predominantly CD8+, CD57+, CD28− and perforin+, which differed significantly from the other non‐expanded Vβ populations. The expression of the apoptosis markers Fas (CD95) and bcl‐2 were similar between the expanded and non‐expanded Vβ populations. In conclusion, expanded T‐cell populations were frequent in patients with myeloma, they 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.