SEMIAUTOMATIC QUANTITATION OF MACROPHAGES IN HUMAN RENAL BIOPSY SPECIMENS IN PROTEINURIC STATES

Aims-To develop and validate a rapid and economical semiautomated appr oach to the measurement of immunostainable tissue components which is applicable to routine diagnostic practice. To apply this approach to t he measurement of macrophages in renal biopsy specimens in nephrotic s tates, as protein in the renal tubules may induce macrophage infiltrat ion, and the morphology of macrophages in tissue sections does not len d itself to cell counting. Methods-Macrophages were identified by immu nostaining with pan-macrophage marker, followed by digital image captu re and analysis using a macro procedure written for the freeware image analysis program NM-Image. Results-The method was rapid, robust and a ccurate to within the Limits imposed by sampling error inherent in the use of small needle biopsy specimens. Very few macrophages are found in normal kidney (mean volume fraction (+/-95% confidence limits) 0.04 % (0.02%)) but infiltration of macrophages was detected in minimal cha nge nephropathy (0.29% (0.12%)) and in membranous glomerulonephritis ( 0.42% (0.11%)). A statistically significant correlation was found betw een macrophage volume fraction and weight of proteinuria in minimal ch ange nephropathy but not in membranous glomerulonephritis. Correlation s were found in both diseases between macrophage volume fraction and s erum creatinine at time of biopsy. Conclusions-The equipment is inexpe nsive and measurement takes less than one minute per biopsy specimen. The results indicate that macrophage infiltration is part of the patho logical process in minimal change nephropathy and membranous glomerulo nephritis. The correlation with creatinine at time of biopsy suggests that renal impairment in minimal change nephropathy may result from in filtration by immunologically active cells and not merely from haemody namic changes in nephrons. However, the correlation is not close, indi cating that the relation between macrophage infiltration and disease s everity is not a simple one.