Bone Marrow Reaction in Chronic Graft-Versus-Host Disease.

Hematopoiesis of the host is a primary target organ of the graft-versus-host reaction. However histological analyses of the bone marrow are rarely reported. Here we report histological changes in the bone marrow of patients (pts) with and without chronic graft-versus-host disease (cGvHD). Bone marrow biopsies were obtained between 101 days and 4623 days (median:419 days) after transplantation as part of a controlled prospective phase ll study of patients with osteopenia/osteoporosis after allogeneic hematopoietic stem cell transplantation (HCT). Previously we reported an increased density of microvessels using an antibody against v. Willebrand factor (vW) (

1. neither aGvHD nor cGvHD;

2. no cGvHD but acute GvHD before entry;

3. cGvHD limited;

4. cGvHD extensive without immunosuppression;

5. cGvHD extensive with immunosuppression.

Results: In the first biopsies the content of CD34+, vW+ microvessels and T-S cells were significantly higher in pts with cGvHD (group 3–5) than in those without cGvHD (group 1–2) (21,3 vs 8,2 p=0,03; 22,0 vs 9,2 p=0,002 respectively 106,2 vs 32,1 p=0,04). In the second biopsies these parameters were also increased in cGvHD: CD34+ (18,3 vs 11,2 p=0,02), vW+ (17,3 vs 9,0 p=0,08) microvessels and T-S cells (63,2 vs 37,8 p=0,27). The increased density of CD34+ and vW+ microvessels correlated with the number of T-S cells (p=0,05). As compared to normal controls we observed a significantly higher content of vW+ microvessels in all groups of transplanted pts (16,9 vs 4,2 p=0,03). In pts with cGvHD (group 3–5) CD34+ and vW+ microvessels were further increased (p=0,02 respectively p=0,002). At the time of the first biopsy the absolute T-S cell content in peripheral blood was moderately increased in group 5 (1124/ul) and minimally increased in group 2 (993/ul) (normal 270 – 880), whereas the overall T cell (CD3) content was normal in all groups. The percentage of activated T-S (HLA-DR+) cells was increased in all groups of transplanted pts (61,8% vs normal =33%; p=0,05). After two years T-S cells content was reduced in pts under immunosuppressive therapy (group 5) (1415 vs 900/ul; p=0.000) but remained increased over the norm. In group 4 T-S cell content was increased over the norm (800 vs 920/ul; p=0,043). In conclusion, sequential immunohistology and immunocytology analyses on bone marrow biopsies and peripheral blood provide evidence for the existence of a chronic graft-versus-host reaction of the bone marrow in pts with cGvHD. This is characterized by an increased content of CD34+ and vW+ microvessels and an increased content of T-S cells at least initially. However this reaction does not lead to a generalized hematopoietic insufficiency.