Renal allograft rejection: immunohistochemistry of inflammatory cellular subsets and vascular lesions.

We have examined sixty-seven surgically removed allograft kidneys to identify the different leukocyte subsets of interstitial infiltration and the early vascular lesions which characterize renal allograft rejection. Histochemical and immunohistochemical results (mouse monoclonal antibodies anti: Leu 1, Leu 3a-3b, Leu 7, Leu 2a, OK Ia-Dr, OKB2, Leu M1, Leu M3; rabbit heteroclonal antibodies anti -: IgA, IgG, IgM, C3, fibrinogen, lysozyme; lectins-ABC: RCA, WGA, UEA) and routine histochemical staining have shown an increase of T-helper and T-activated lymphocyte subsets in acute rejection. Neutrophilic leucocytes were present in hyperacute rejection; macrophages were also noted. In chronic rejection, several lymphocyte subsets, in different ratios, were identified. Monocyte/macrophage leukocytes were the most abundant cell population. IgA deposits were noted on tubular epithelia in hyperacute and chronic rejections. IgM deposits were observed in vascular walls in chronic rejection. C3 and fibrinogen deposits were seen in glomerular capillaries and in arterial walls, although in different ratios, in all cases of renal allograft rejections. We have generally seen weak reactions to IgG deposits. Histochemical analysis of lectin receptors has given different results according to the type of rejection considered. In hyperacute rejection, receptors for WGA were found both on glomerular endothelial cells and on the tubular brush border. In the latter, receptors for RCA were also found. In acute rejection, receptors for UEA and WGA were found in a lower number of cases of acute vascular rejection. In acute cellular rejection, receptors for RCA, UEA and WGA were recognized in tubular epithelia. In acute vascular rejection, as well as in chronic rejection, only receptors for WGA were present on tubular epithelia and on capillary loop endothelium. The use of anti-human lysozyme antibodies has yielded the following results: in acute and hyperacute rejection, when renal failure occurred, we saw a high ratio of lysozyme, either coarsely granular or diffuse in the proximal tubular epithelia. Lysozyme was found in myelocyte/macrophage cells within capillary loops and arterial walls, when acute necrotizing vasculitis was present. In acute rejection, proximal tubular cells were lysozyme-negative or lysozyme-positive only segmentally, especially when obliterative vasculitis by fibrointimal proliferation was present and renal function progressively failed. In most of the chronic rejections, tubular cells were lysozyme-negative.