Peripheral blood lymphocyte subsets in multiple myeloma and monoclonal gammopathy of undetermined significance.

Peripheral blood lymphocyte subsets were analysed by flow cytometry and compared among 43 patients with untreated multiple myeloma (MM), 16 patients with monoclonal gammopathy of undetermined significance (MGUS) and 26 controls. The age and sex distributions of the patients and controls were comparable, which is important, since in the controls there was a significant effect of age and/or sex on the number of CD3+, CD57+, CD8+57+, CD16+ and CD3-56+ lymphocyte subsets, and on the CD4+/CD8+ and CD4+Leu-8+/CD4+ ratios. In MM, the number of CD8+ and CD57+ cells and the CD4+/CD8+ ratio were related to the clinical stage. The number of CD20+, CD3+, CD4+, CD16+ and CD3-56+ cells and the CD3+/CD20+ ratio were significantly different in MM patients compared to age- and sex-matched controls as was the number of CD3+ and CD4+ cells of MGUS patients compared to controls. Further, there were significant differences in the CD3+/CD20+ ratio between MM and MGUS patients and between stage I MM and MGUS. The role of peripheral blood lymphocyte subsets in differentiating monoclonal gammopathies merits further study.