Immunoglobulin-containing plasma cells in chronic parotitis and malignant lymphomas of the parotid gland. Comparing immunocytochemical observations of frequency and localization.

IgA-containing plasma cells in the periductal gland tissue are part of the special secretory immune system of the salivary glands. The reaction of Ig-containing plasma cells (localization, frequency, specific Ig-content) was analyzed by the indirect immunoperoxidase method in chronic recurrent parotitis (9 cases), chronic myoepithelial parotitis (benign lymphoepithelial lesion, Sjögren's syndrome; 8 cases), and malignant lymphoma associated with chronic myoepithelial parotitis (11 cases). The following results were obtained: 1. In chronic recurrent parotitis, parallel to the increase in IgA in the salivary secretion, a marked multiplication of IgA-containing plasma cells was found in the inflammatory infiltrate and the remaining non-inflamed periductal parenchyma of the parotid gland. In the marginal zone of inflammation, a slight increase of IgG-containing plasma cells was also observed. 2. In chronic myoepithelial parotitis, the total plasma cellular infiltration was slightly less distinct than in chronic recurrent parotitis. The most remarkable increase in Ig-containing plasma cells developed in the marginal zones--away from the myoepithelial cellular islands--as well as in the area of ductular proliferations, and was characterized by a strong increase of IgG-containing plasma cells. At the same time, a slight increase of IgM-containing plasma cells was observed. No plasma cells were found in the myoepithelial cellular islands. 3. In the malignant lymphomas associated with myoepithelial parotitis, which were mainly highly differentiated lymphomas (immunocytomas, centrocytic-centroblastic lymphomas) and rarely poorly differentiated immunoblastic lymphomas, there was a distinct decrease of IgG-containing plasma cells when compared with the numbers in this group without lymphoma. The differing degrees of prevalence and Ig-content of the plasma cells partly describe the change taking place in the local secretory immune system of the parotid gland. The possible relationships between chronic recurrent parotitis and auto-immune myoepithelial parotitis on one hand and the stages of transition (prelymphoma) to malignant lymphoma on the other, are discussed.