INCREASED RATES OF POLYMERIC IGA SYNTHESIS BY CIRCULATING LYMPHOID-CELLS IN IGA MESANGIAL GLOMERULONEPHRITIS

Abstract

Recently the existence of high levels of polymeric IgA was described, partially as immune complexes, in the serum and kidney from patients with IgA mesangial glomerulonephritis. As these patients often have macroscopic hematuria following upper respiratory tract infections, circulating lymphocytes from secretory tissues after viral stimulus could possibly produce in these patients a large amount of polymeric IgA. Peripheral blood lymphocytes (PBL) from patients and controls were cultured for 7 days in the presence or absence of pokeweed mitogen (PWM). In cell culture supernatants Ig synthesis was measured by radioimmunoassay and the proportion of polymeric and monomeric IgA was determined on Ultrogel Ac A22 column. There was no difference in spontaneous production of Ig between patients and controls. The IgA synthetized by PWM-stimulated PBL was significantly higher in patients than in controls. The percentages of IgA with MW of 600,000-250,000 after supernate fractionation were significantly higher in patients than in controls. The true nature of polymeric IgA was confirmed by their ability to bind secretory component, the existence of covalent structures and the decrease of the larger forms of IgA after reduction and alkylation. The percentage of IgA producing cells binding secretory component was significantly higher in patients than in controls (69 .+-. 21 vs. 44 .+-. 27) after 7 days of culture. IgM and IgG produced in patient culture were similar to controls. Mitogen stimulated PBL from patients with Berger''s disease synthetized a large amount of true polymeric IgA. Thus, a similar situation could occur in vivo after viral or other stimuli.