The relationship of infiltrating renal leucocytes to disease activity in lupus and cryoglobulinaemic glomerulonephritis.

In order to evaluate the contribution of cellular immune mechanisms in the pathogenesis of immune complex-mediated glomerulonephritis, renal biopsies from 18 patients with lupus glomerulonephritis and 26 with cryoglobulinaemic glomerulonephritis were studied. Leucocyte profiles including T cell subsets and 'activated' macrophages within both glomeruli and interstitium were determined, using a panel of monoclonal antibodies as markers, and a sensitive 4-layer peroxidase technique to localize these within tissues. The infiltrating leucocytes were correlated with clinical, histological and immunological parameters of disease activity. Normal glomeruli contained few leucocytes though normal interstitium did (145 +/- 30 mm2), made up predominantly of T lymphocytes and macrophages. There was a significant increase in intraglomerular leucocytes in both systemic lupus erythematosus 4-fold, and essential mixed cryoglobulinaemia 7-fold, as compared to normal. These leucocytes consisted mainly of macrophages, and particularly in cryoglobulinaemia of 'activated' macrophages as demonstrated by their surface expression of the procoagulant tissue factor recognized by the A13 monoclonal antibody. In cryoglobulinaemic glomerulonephritis (GN) there was also a significant increase in T lymphocytes due to a predominance of suppressor-cytotoxic cells (OKT8+). There was a significant increase in interstitial leucocytes in both diseases, lymphocytes (mainly OKT8+ve), and macrophages (mainly 'activated' A13+ve). There were significant positive correlations between disease activity and interstitial leucocyte infiltration including, in lupus nephritis, degree of proteinuria and total leucocytes, hypocomplementaemia and T lymphocytes, increased numbers of monocytes and lymphocytes with a higher histological index of activity, and in cryoglobulinaemic GN of T lymphocytes and proliferative lesions, and T lymphocytes and C1q deposition. This study has demonstrated the importance of the interstitium in the pathogenesis of both diseases, delineated the presence of both T lymphocytes and activated monocytes which make cell-mediated immune mechanisms feasible, and linked the presence of immune mediators to disease activity.