Limbus damage in ocular graft-versus-host disease.

Graft-versus-host disease (GVHD) is the major cause of morbidity and mortality among patients undergoing allogeneic hematopoietic stem cell transplantation. Although animal models have been clearly established for the study of skin, liver, and gut, currently there is no equivalent experiemental model for analyzing ocular involvement, which is rather common, especially among patients diagnosed with chronic GVHD. In the current study we have developed a murine model of ocular GVHD and, for the first time, we describe the histopathologic features involving cornea and limbus, which could play a role in the physiopathology of the disease at the ocular level. Our results represent a major finding that allows us to define a model for evaluating new therapeutic strategies for treating ocular GVHD prior to their use in clinical setting.

Chronic graft-versus-host disease: Pathogenesis and clinical management.

Chronic graft-versus-host disease (cGVHD) is the most common and severe complication among patients surviving >100 days after allogeneic transplantation. It starts with the expansion of donor T cells in response to alloantigens or autoantigens that are unchecked by normal thymic or peripheral mechanisms of deletion. The T cells induce damage to target organs either directly through cytolytic attack, inflammatory cytokines and fibrosis, or by promoting B cell activation and production of autoantibodies. HLA disparity, donor and patient age and sex, source of progenitor cells, graft composition and previous acute GVHD are the main factors that predict the risk of developing cGVHD. Once the diagnosis has been established, patients needing treatment (extensive cGVHD) must be identified. Poor prognostic factors such as extensive skin involvement, thrombocytopenia and progressive-type onset of cGVHD must be considered in order to define the immunosuppressive treatment requirements. Prednisone, together with a calcineurin inhibitor such as ciclosporin or tacrolimus, can be considered the standard regimen as primary treatment for cGVHD. Using that approach, among high-risk patients (identified as those with extensive cGVHD plus thrombocytopenia) 3-year survival reached 52%. Concerning salvage regimens, to date there is no clear standard regimen for cGVHD treatment, the best choice being to enter the patient into a clinical trial. Immunosuppressive drugs that inhibit T cell activation, proliferation or survival, such as mycophenolate mofetil, the anti-interleukin-2 alpha receptor antagonist daclizumab, sirolimus (rapamycin), extracorporeal photopheresis and pentostatin (deoxycoformycin), among other agents, have been used with a very wide range of complete responses ranging from 5% to 50%. In addition, anti-cytokine or B cell inhibitors such as etanercept or rituximab have also been evaluated. The severe immunosuppression induced by those drugs increases the risk of infectious complications and may have a deleterious effect on the graft versus tumour effect after transplant so that newer strategies based on the selective depletion of alloreactive T cells and induction of more specific immunotolerance against host tissues are required.

Long-term bone marrow culture data are the most powerful predictor of peripheral blood progenitor cell mobilization in healthy donors.

BACKGROUND AND OBJECTIVES: There is wide interindividual variation in progenitor cell mobilization. The present study was aimed to analyze steady state hematopoiesis in healthy donors and its influence on hematopoietic progenitor cell (HPC) mobilization. DESIGN AND METHODS: Bone marrow (BM) was aspirated from 72 healthy donors prior to administration of recombinant human granulocyte colony-stimulating factor (G-CSF). Analyses of CD34+ cells and semisolid cultures as well as long-term cultures were performed from BM or leukapheresis products. RESULTS: Male donors showed a higher number of BFU-E (p=0.007) and committed progenitors (p=0.05), a better stromal layer (p=0.02), and higher long-term bone marrow culture (LT-BMC) counts (p<0.05) when compared to those in female donors. When correlating the culture pattern of the BM with the data from the leukapheresis products, we observed that the number of the immature progenitors in BM correlated significantly with both the number of CD34 + cells and CFU-GM in the first leukapheresis. Univariate analysis revealed that the following variables had a beneficial impact on the number of CD34+ cells: male sex, body weight >73 Kg, G-CSF schedule and results of LT-BMC, although in the multivariate analysis only the number of CFU-GM obtained after LT-BMC showed a significant influence (p<0.001). INTERPRETATION AND CONCLUSIONS: These results confirm the interindividual variation in HPC mobilization among healthy subjects, with LT-BMC counts being the most reliable predictor, expressing the behavior of the immature progenitors and their relationship with the microenvironment.