Natural killer cells and CD56+ T cells in the blood of multiple myeloma patients: analysis by 4-colour flow cytometry.

The blood of multiple myeloma patients was examined for non-MHC-restricted cytotoxic lymphocytes. Four colour flow cytometry was used to phenotype the cells within a light scatter gate large enough to include all lymphocytes. NK and T cells were identified using CD16, CD56, and CD3 antibodies, and myeloid cells with CD13 and CD14 antibodies. Three subpopulations of NK cells and 3 subpopulations of CD16+ or CD56+ T cells were enumerated. The CD56+ NK and T cells were also examined with CD69, CD25, and anti-HLA-DR antibodies to assess their activation state. We found no evidence that either the percentage or the absolute number of any subpopulation of the NK cells or CD56+ T cells correlated with disease activity. Neither did we find any significant abnormalities in the numbers of activated CD56+ NK or T cells. We conclude that it is unlikely that circulating non-MHC-restricted cytotoxic lymphocytes are responsible for maintaining disease stability in myeloma patients with indolent disease.