T-lymphocyte reconstitution in recipients of bone marrow transplants with and without GVHD: imbalances of T-cell subpopulations having unique regulatory and cognitive functions

The development of T lymphocytes in 34 patients engrafted with allogeneic bone marrow was studied by indirect immunofluorescence using mouse monoclonal antibodies. Two antibodies, termed anti-Leu-1 and anti-Leu-4, react with distinct membrane components expressed by all peripheral T cells, whereas two other antibodies, termed anti-Leu-2a and anti-Leu-3a. react with complementary subsets of Leu-1 + and Leu-4+ lymphocytes. The Leu-2a + 3a– (Leu-2) subset contains suppressor/cytotoxic T cells, and the Leu-2a – 3a+ (Leu-3) subset contains helper T cells. The ratio of Leu-2/Leu-3 T cells was elevated in nearly all patients studied during the first month of engraftment, but this ratio subsequently returned to normal in patients with an uncomplicated course or with solved acute GVHD. In contrast, a deficiency of helper T cells with a resultant preponderance of suppressor/ cytotoxic T cells persisted in all patients studied with both acute and chronic GVHD after the first month. The implications of these findings in regard to the functions of these cells in vitro are discussed.