Changes in rectal leucocytes after allogeneic bone marrow transplantation.

Using immunohistological techniques the number of leucocytes present in the epithelium and lamina propria of the rectal mucosa were assessed in 16 allogeneic bone marrow transplant recipients, with and without evidence of graft-versus-host disease (GVHD), and compared with a non-transplant group of patients. Samples were obtained between 15 and 198 days after transplant. In marrow recipients without GVHD, compared with non-transplant cases, there was a decrease in T lymphocytes in the lamina propria due to a reduction in the helper-inducer (T4+) subset with no change in suppressor-cytotoxic (T8+) cells or epithelial leucocytes. In GVHD, the number of T lymphocytes increased both in the lamina propria and epithelium due to an increase in T8+ cells with no change in T4+ cells. Lymphocytes did not express the activation markers detected by Tac, OKT10 or HLA-DR. Macrophages and natural killer cells were not changed after transplant or in GVHD. Epithelial HLA-DR expression was detected in seven out of eight in the GVHD group, three out of eight in the non-GVHD transplant group and two out of eight in the non-transplant cases. These findings show several differences from those we have observed in cutaneous and hepatic GVHD. Although elevated numbers of T8+ cells are common to GVHD in all three sites, the precise role of these cells in producing epithelial damage is not clear.