Importance of plasma cells in the infiltrate of renal allografts. An immunohistochemical study.

The cellular infiltration in 42 needle and wedge biopsies of transplanted kidneys was investigated immunohistochemically. The percentages of helper/inducer (CD 4+) cells, suppressor/cytotoxic cells (CD 8+), B lymphocytes, macrophages, plasma cells (Pc) and granulocytes were determined. The proportions of the various inflammatory cell populations were established in acute interstitial rejection (AIR), acute vascular rejection (AVR), chronic rejection (CR) and cyclosporin A nephrotoxicity (CsAN). The most prominent differences were detected as regards the Pc, whose number was much higher in CR than in AIR, AVR or CsAN. The striking difference between CR and CsAN in the number of Pc may be of differential diagnostic importance: the presence of many Pc in the biopsies can be regarded as a sign of CR. Over 80% of the Pc in CR contained IgG, whereas in chronic interstitial nephritis (CIN) the IgA-positive Pc predominated. In AIR, AVR and CsAN, too, the majority of the Pc contained IgG, but the numbers of IgM and IgA-positive cells were also relatively high. The great number of IgG-positive Pc indicates an important role of a secondary type humoral immune response in CR.