Severe Aplastic Anaemia Treated with Anti-Lymphocyte Globulin

Delayed activation-induced T lymphocytes death in aplastic anemia: related with abnormal Fas system

OBJECTIVES

To quantitate apoptosis and Fas antigen expression of T lymphocytes by activation in aplastic anemia (AA) and compare with that of normal controls and completely-recovered AA, and to investigate the apoptotic sensitivity to anti-fas antibody of activated T lymphocytes in AA.

METHODS

We studied the expression of Fas antigen on fresh T lymphocytes of twenty patients with AA [13 newly diagnosed, 7 recorvered AA after immunosuppressive therapy (IST)], and investigated the activation-induced cell death (AICD) and Fas expression by activation [interleukin-2 (200 U/ml) and phytohemagglutinin (50 micrograms/ml)] in 5 newly-diagnosed AA, 5 normal controls and 5 AA in complete response (CR). Apoptotic sensitivity to anti-Fas antibody was assessed by the time-course kinetics of induction of cell death by anti-Fas antibody (500 ng/ml).

RESULTS

There was no significant difference of Fas antigen expression on freshly-isolated T lymphocytes among newly-diagnosed severe AA, normal controls and patients with AA in CR after IST. In normal controls, T lymphocytes death was greatly increased at 3 days of activation, and Fas antigen expression on T lymphocytes was increased above baseline at day 1 of activation. In contrast, in newly-diagnosed AA, T lymphocytes showed delayed cell death, which correlated with a slowed increase of Fas antigen expression by activation. Also, anti-Fas antibody sensitivity of activated T lymphocytes was decreased in newly-diagnosed AA. In completely recovered AA, these abnormal AICD and Fas antigen expressions by activation were recovered to normal range.

CONCLUSIONS

Abnormal AICD plays a role in the immune pathophysiology of AA, and defective Fas system is involved in this process.

No evidence for gamma-interferon mediated haematopoietic inhibition by T cells in aplastic anaemia: an observation in the course of immunosuppressive therapy

Two patients with aplastic anaemia were treated with immunosuppressive agents and peripheral blood T cells were cryopreserved serially. Inhibitory activity of T cells to autologous CFU-E, gamma-IFN production by T cells and T cell subpopulations were assayed after remission. Inhibitory activity to autologous CFU-E was not correlated with the numbers or ratios of T cell subpopulations. gamma-IFN production by T cells were within the normal range when inhibitory activity was found. In addition, gamma-IFN production increased after haematopoietic recovery. These findings suggest that gamma-IFN is not a soluble mediator of T cell-mediated haematopoietic inhibition in aplastic anaemia.

T cell-mediated inhibition of haematopoiesis in aplastic anaemia: serial assay of inhibitory activities of T cells to autologous CFU-E during immunosuppressive therapy

T cell-mediated inhibition of autologous erythroid colony formation was found in two patients with aplastic anaemia. Each patient was treated separately with ALG and methylprednisolone. Peripheral blood T cells were cryopreserved serially during the course of the disease. The inhibitory activity of T cells was assayed after remission using autologous bone marrow. The inhibitory activity of T cells was lost following the treatment and preceded haematopoietic recovery.

Pure red cell aplasia: relationship between inhibitory activity of T cells to CFU-E and erythropoiesis

T cell-mediated inhibition of autologous late erythroid colony formation was found in two patients with PRCA. Each patient was treated separately with immunosuppressive agents, ALG, bolus methylprednisolone or cyclophosphamide. Cyclophosphamide was the most effective among these immunosuppressive therapies. Peripheral blood T cells, which were taken serially from the patients during the course of the disease, were cryopreserved until use. The inhibitory activity of T cells was assayed after remission using autologous bone marrow. It was found that the decrease of inhibitory activity was closely correlated with clinical improvement and that the effectiveness of the immunosuppressive therapy on inhibitory activities of T cells differed between therapies. These findings suggest that T cell-mediated inhibition of erythropoiesis may be pathogenetic for PRCA in some patients.

Bone marrow failure in dyskeratosis congenita

We report a case of dyskeratosis congenita ( DCG ) with neutropenia, lymphocytopenia and thrombocytopenia. Peripheral blood T lymphocytes (T cells) were proved to have a suppressive effect on the colony forming unit granulocyte-macrophage (CFU-GM). Splenectomy caused a transient increase of neutrophil count with the disappearance of the suppressive T cell activity. However, pancytopenia recurred without re-appearance of suppressive T cell activity.