Age-related factors in cyclosporine-induced syngeneic graft-versus-host disease: regulatory role of marrow-derived T lymphocytes

VHD. Further studies were 89 Fischer and Hess undertaken to phenotypically characterize the cells contained in fraction 25 of marrow from both mature (6 mo) and immature (1 mo) Lewis rats. Single-color flow cytometric analysis demonstrated that fraction 25 from animals 6 mo of age (mean of three experiments) had a predominance of cells with mature T lymphocyte markers : 22.6% OX19+, 12.3% CD4+, and 8.4% CD8+ . (Table 3 ) . Fraction 25 from 1-moold animals had 12.5% cells with mature T cell markers, and a predominance of B cells (OX 33+) and cells expressing OX7 or Thy-1.1 (B cells also express OX7). There was also a significant percentage ofcells not staining with any markers. The greatest difference appeared to be the reduced number of T cells in fraction 25. Comparatively, the marrow R/O and 29 fractions from both groups had minimal total T cells defined by staining with OX19 (fraction 29 <15% ; R/O <5%). Furthermore, fraction 29 is only a small percentage (11-16%) of the entire elutriated marrow.