Reconstitution of the CD45RO(+) and CD20(+) lymphoid marrow population following allogeneic bone marrow transplantation for Ph+ CML

Following bone marrow transplantation (BMT) investigations on the recovery of the B and T lymphocyte populations have focused on the peripheral blood and only marginally regard the bone marrow, An immunohistochemical and morp hometric study was performed on 352 trephine biopsies derived from 123 pati ents with chronic myelogenous leukemia (CML) at standardized endpoints befo re and after allogeneic BR IT and compared to a control group. The purpose of this investigation was to quantify the B-CD20(+) and TCD45RO(+) lymphocy te subsets and to determine possible relationships with the occurrence of a cute and chronic GVHD, Moreover, we studied the dynamics of lymphocyte repo pulation in the post-transplant period, correlations with the total periphe ral lymphocyte count and differences associated with sibling vs alternate H LA-compatible (unmanipulated) marrow grafts. Morphometric analysis revealed a very fast regeneration of CD45RO(+) and CD20(+) marrow lymphocytes in th e first 2 weeks following BMT. In less than 2 months, in most patients, the post-transplant quantity of lymphocytes was comparable to that of the norm al bone marrow, This finding was opposed to the profound depression of the absolute lymphocyte count in the peripheral blood. No relevant relationship s could be calculated between engraftment status and the lymphocyte repopul ation in the bone marrow. On the other hand, significant correlations were calculable between the development of (chronic and acute) GVHD including se verity with the number of CD45RO(+) lymphocytes, In non-related graft const ellations a more frequent evolution of acute grade III + IV GVHD was detect able. This complication was accompanied by an increased quantity of CD45RO( +) lymphocytes in the marrow.