The effect of antithymocyte globulin on abnormal lymphocyte transformation in patients with aplastic anemia

Anti-thymocyte globulin treatment for aplastic anemia

20 patients with severe aplastic anemia were treated with anti-thymocyte globulin (ATG), 6 of them in combination with haplo-identical bone marrow. 7 patients (35%) showed a good clinical response within 6 months; they were off transfusions and had greater than or equal to 0.8 x 10(9)/l neutrophils. ATG had the greatest effect on red-cell production and the least on platelet production. The hematological recovery with ATG could not be predicted from the bone-marrow histology, CFU-c growth, or clinical data. However, patients with strong HLA antibodies seemed to respond more often. The actuarial survival was 55% at 5 years. Under intensive supportive care, even 7 out of 12 non-responders were alive after 1 year. ATG appears to be a useful form of therapy for patients with severe aplastic anemia who are not candidates for bone-marrow transplantation.

Environmental factors in haemopoietic failure in humans

Aplastic anaemia can be defined as pancytopenia in the presence of a hypoplastic bone marrow and in the absence of leukaemia or malignant infiltration. Most cases have been attributed to an intrinsic defect in the pluripotential haemopoietic stem cell; however, stem cell suppression or a defect in the marrow environment would also produce the symptoms of aplasia. In vitro culture systems have been used to explore these possibilities and have provided evidence that the syndrome known as aplastic anaemia includes several distinct disease processes. These include primary failure of the haemopoietic stem cell and the suppression of stem cell function by cellular, humoral or other environmental factors. This heterogeneity provides the background for attempting to treat the disease by bone marrow transplantation, immunosuppression or stimulation of haemopoiesis.