Surface markers on peripheral blood lymphocytes were studied in Sjögren's syndrome. Cells bearing IgG, IgA, IgM and IgD were identified with monospecific fluorescent antiserums. In five of seven patients the frequency of cells identified with at least two anti-heavy-chain reagents was elevated. In two of these patients striking elevations were seen in the frequency of lymphocytes bearing each of the heavy-chain classes, the sum of the number of cells binding individual anti-heavy-chain serums being about four times greater than the apparent number of B lymphocytes as identified both with an anti-Fab reagent and by the binding of aggregated γ-globulin. The cells binding anti-heavy-chain serums were identified as B lymphocytes by doubling labeling procedures. These data indicate that individual B lymphocytes in some patients with Sjögren's syndrome bear multiple classes of heavy chains, an abnormality that has been noted by others in some patients with lymphoma. This association is of interest since there is a spectrum of benign to malignant lymphoproliferation in Sjögren's syndrome. (N Engl J Med 289:823–827, 1973). HUMAN peripheral blood lymphocytes form a heterogeneous population of cells with regard to origin and function. Subgroups of these lymphocytes may be characterized by the presence of distinct surfacemembrane markers. Thus, evidence collected from studies in laboratory animals and patients with immunodeficiency diseases indicates that cells bearing easily detectable surface immunoglobulin (Ig) are thymus-independent, bursal-equivalent (B) lymphocytes1 2 3 4; such cells can be further characterized on the basis of the class of Ig that they bear. B lymphocytes also have a membrane receptor allowing them to bind antigen–antibody complexes and aggregated γ-globulin.5 This receptor is distinct from the well studied complement.
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