IMMUNOHISTOCHEMICAL CHANGES IN SIGMOID COLON AFTER ALLOGENEIC AND AUTOLOGOUS BONE-MARROW TRANSPLANTATION

Aim-To determine whether there are characteristic immunohistological c hanges in the colonic mucosa in acute graft versus host disease (GvHD) . Methods-Consecutive allogeneic (n=11) and autologous (n=11) bone mar row transplant recipients underwent endoscopic biopsy of sigmoid mucos a before transplant and on day 30 post-transplant. Immunohistochemical staining and quantitation of intraepithelial and lamina propria monon uclear cells were undertaken using a panel of monoclonal antibodies an d a Streptavidin-biotin alkaline phosphatase staining technique. Resul ts-In the allogeneic group (nine of whom had clinical acute GVHD) ther e was a fivefold increase in lamina propria CD16 + mononuclear cells ( 3.1 + 4.3 to 17.0 + 12.2 per 100 lamina propria nucleated cells), comp ared with autologous transplant recipients in whom this rise was twofo ld (5.5 +/- 4.6 to 10.6 +/- 7.1 per 100 lamina propria nucleated cells ). The CD16 + mononuclear cells had morphological appearances of tissu e macrophages, but in neither the allogeneic nor autologous groups was there an increase in total macrophage numbers (CD14+). In patients wi th acute GVHD the lamina propria CD4+:CD8+ lymphocyte ratio fell (1.97 + 1.12 to 1.07 + 1.01), primarily because of a fall in the number of lamina propria CD4+ lymphocytes. In both allogeneic and autologous gro ups there was a fall in intraepithelial lymphocyte numbers, but there was no change in CD19+ (B cell), CD25+ (interleukin-2 receptor positiv e) or CD56+ (natural killer) cell numbers. Conclusion-Following bone m arrow transplantation, there appears to be upregulation of lamina prop ria tissue macrophage CD16 (an Fc receptor for IgG), a change which is more noticeable after allogeneic transplantation and which may be rel ated to the development of acute GVHD. In patients with acute GvHD the re was a fall in the lamina propria CD4+:CD8+ lymphocyte ratio. If the se changes are functionally important, they may have significant impli cations for understanding the pathogenesis of GVHD.