Quantification of plasma cells in labial salivary glands: increased expression of IgM in Sjögren's syndrome

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Abstract
Plasma cells expressing IgG, IgA and IgM were quantified in labial salivary glands from patients with Sjogren''s syndrome (SS) and compared with glands showing non-specific inflammatory changes and normal controls. In all glands the predominant isotype was IgA but in SS there was a significant increase in both the number and proportions of IgG and IgM positive cells (P < 0.002). In particular, all SS cases contained greater than 10% IgM positive cells (mean = 26.8 .+-. 15.5). The results suggest that accumulation of IgM positive plasma cells may be a specific finding in SS and support the concept that the glandular lesions may be a site of B-cell clonal expansion. Since most B-cell hyperproliferative states in SS, including lymphoma, are associated with synthesis of IgM simple quantification of plasma cells may have important diagnostic and prognostic significance.