Allogeneic hematopoietic cell transplantation offers high cure rates for patients with hematological and oncological diseases. Graft-versus-host disease (attack of donor's white blood cells on patient's tissues) is a serious complication also affecting the patient's immune system. Therefore, patients in the early phase after allogeneic cell transplantation are at high risk for severe infectious complications. So far, no predictive biomarkers for the development of the chronic form of graft-versus-host disease are available. By analysing serially immune cell populations of the peripheral blood we will investigate whether certain subsets of cells are associated with development of chronic graft-versus-host disease. In addition, the patients' immune regeneration will be evaluated by serial analyses of peripheral blood immune cell populations 3 months to 2 years after allogeneic cell transplantation.

Inclusion Criteria:

• Receiving grafts from either HLA-identical sibling donors or HLA-matched unrelated donors
• Receiving grafts from HLA-mismatched sibling donors or HLA-mismatched unrelated donors
• Receiving either bone marrow, peripheral blood stem cells or cord blood grafts
• Alive on day 100 after transplant
• Age 18 years or above
• Signed written informed consent

Exclusion Criteria:

• Lymphocytopenia not allowing immunophenotyping
• Treatment with rituximab after HSCT until study entry
• Hepatitis B and C, HIV infection
• Secondary posttransplant malignancies including EBV-lymphoproliferative disease
• Karnofsky score of 30 or below
• Absence of informed consent

all consecutive patients after allogeneic hematopoietic cell transplantation