Abstract
A case of malakoplakia of the kidney is presented. Purified plasma membranes from the malakoplakia lesions stimulate blast transformation of the patient's autologous lymphocytes indicating the persistence of bacterial antigens which stimulate primarily thymus-derived lymphocytes. The skin test immunologic competence of the patient and the peripheral blood monocyte chemotactic response were normal. The pathologic findings and these immunologic studies are discussed in relation to xanthogranulomatous pyelonephritis and megalocytic interstitial nephritis and the pathogenesis of this disease.