[Immunologic reactions following heart transplantation and their detection]

Transplantation antigens of the major histocompatibility complex are able to stimulate the rejection of the graft. Class I and class II antigens presented by dendritic cells to the host macrophages are found on parenchymal cells (class I) or combined on all passenger leucocytes. Humoral factors like interleukin 1 produced by the macrophages activate the helper-lymphocyte subpopulation. The cytotoxic effector cells but also antibody producing B-cells receive their signal (interleukin 2) from the helper cells. Cellular and humoral mechanisms attack the vascular endothelium and the endocard first. Typical perivascular infiltrates or antibodies on the sarcolemm of myocard fibres and the intima herald the two types of rejection. The activated lymphocytes and their blast forms recirculate in various amounts in the peripheral blood, reflecting the severity of the event. Hematological evaluation including differentiation of lymphocyte subsets by monoclonal antibodies according to their phenotype seem to be a tool to recognize these mechanisms at an early stage. It is suggested that the optimal therapy and the necessary biopsy can be adjusted even more precisely using this immunological monitoring.