Effect of haematological malignancies and their treatment on host defence factors.

Immunological factors are involved in all aspects of the lymphomas and leukaemias. The aetiology of these diseases is related at least in some cases to immunodeficiency, immunostimulation, autoimmunity and a dysregulation of the immune system. The majority of lymphomas and leukaemias are monoclonal proliferations of the B-lymphocyte series at different stages of maturation while some are derived from T lymphocytes and others have no recognisable B or T-cell markers. Each of the lymphoid malignancies has a characteristic and unique pattern of immunological deficiency, suggesting a unique aetiology. Hodgkin's disease and histiocytic lymphoma, the acute leukaemias and chronic myelogenous leukaemia have predominantly cell-mediated immune deficiencies, while lymphocytic lymphoma, chronic lymphocytic leukaemia, multiple myeloma, and the plasma cell dyscrasias have predominantly humoral immune deficiencies. There is a relationship between immunocompetence and prognosis and between immunocompetence and extent of disease in the lymphomas and leukaemias. Immunocompetent patients have a better prognosis and more limited disease than immunoincompetent patients. Therapy for these diseases profoundly suppresses host defence mechanisms, particularly those which are cell-mediated. Ability to resist or recover from this immunosuppression is also associated with an improved prognosis. Lymphoma and leukaemia also induce a tumour-specific immune response in the tumour-bearing host and this also correlates with prognosis. These factors form a rational basis for immunotherapy and indeed lymphomas and leukaemias respond to active nonspecific immunotherapy with BCG and active specific immunotherapy with tumor cells resulting in prolongation of remission duration and survival.