Clustering of IgA-producing immunocytes related to HLA-DR-positive ducts in normal and inflamed salivary glands.

Ig-producing immunocytes and epithelial expression of secretory component (SC) and HLA-DR were evaluated by two-colour immunofluorescence staining in 10 normal and 20 inflamed salivary glands; the latter included specimens from 10 patients with obstructive sialadenitis and 10 with Sjögren's syndrome (SS). Epithelium adjacent to T-cell infiltrates showed extensive co-expression of SC and HLA-DR, suggesting that leucocyte-derived cytokines were responsible for this concurrent up-regulation. Clusters (greater than 2 positive cells) of IgA-producing cells were spatially related to DR-positive ducts. The possibility is discussed that DR-expressing epithelium contributes to local terminal differentiation of IgA-producing plasma cells. A cytokine-mediated up-regulation of SC that simultaneously increases the transport capacity for polymeric IgA would constitute an efficient enhancement of secretory immunity in diseased glandular tissue.