Severe aplastic anaemia treated with anti-lymphocyte globulin. The relationship between clinical course and erythroid colony suppression by T cells.

A 6-year-old girl with severe aplastic anaemia improved promptly after treatment with anti-human lymphocyte globulin (ALG). Blood T lymphocytes were proved to have a suppressive effect on erythroid colony formation. ALG was administered intravenously at a dose of 15 mg/kg/d for 5 d. By the 14th d she showed a prompt increase in the reticulocyte count. Within the next 2 weeks slight increase of the platelet count was observed while the neutrophil count remained unchanged. The suppressive effect of T cells on erythroid colony formation weakened when the reticulocyte count exceeded 100 X 10(9)/l. About 4 months after administration of ALG, a decreased reticulocyte count was observed along with frequent nasal bleeding. Again the T cells exhibited a suppressive effect on erythroid colony formation. The results of serial co-culture studies revealed a close correlation between the T-cell suppressive effect on erythroid colony formation and reticulocyte response. The findings suggest an immune-mediated mechanism for the haematopoietic disorder in this patient.