In vitro tests in severe aplastic anaemia (SAA): a prospective study in 46 patients treated with immunosuppression

Decreased blood natural killer cell activity and immunoglobulin synthesis in vitro in aplastic anemia

Natural killer (NK) cell numbers and T lymphocyte subpopulations in peripheral blood were evaluated in six patients with aplastic anemia (AA). The immunophenotyping results were correlated to in vitro tests of NK cell cytotoxicity against K562 cells and of immunoglobulin (Ig) production after pokeweed mitogen (PWM) stimulation. A significant decrease was found both in the percentage of Leu 11 positive cells and in NK cell activity as compared to age- and sex-matched healthy controls. The decrease in NK cell activity could not be entirely compensated by an increase in effector/target cell ratios, thus suggesting not only a quantitative but also a functional defect in NK cells of the AA patients. Three of four AA patients tested showed no major increase of Ig production after PWM stimulation. All these three patients also had fewer "functional T helper" cells (Leu3+/Leu8-) and increased numbers of T suppressor/cytotoxic cells (Leu2+) when compared to controls. No significant differences in numbers of B lymphocytes (B1+) could be found. Our findings suggest a possible linkage between quantitative and qualitative abnormalities in lymphocyte subsets in aplastic anemia. However, no evidence was found to support the hypothesis of increased NK cell activation behind the hemopoietic depression in this disease.

Allogeneic bone marrow transplantation for severe aplastic anemia: the Hong Kong scenario

Severe aplastic anemia (SAA) is a disease associated with high mortality. For young patients with HLA identical siblings, allogeneic bone marrow transplantation (BMT) offers the best chance of cure. Favourable results have also been reported using immunosuppressive therapy (IST). Transplantation is usually favoured for patients below 45 years of age. We report our experience of 11 allogeneic and one syngeneic BMT for adult Chinese patients with SAA, over a 4-year period from 1991 to 1995. Ten of the 12 (83 per cent) patients had received and failed prior IST including anti-thymocyte globulin (ATG) before being referred for BMT. Neutrophil and platelet engraftment was successful in 11 of them (92 per cent) and nine were completely transfusion independent after transplantation. Their overall 3-year survival was 67 per cent. The compromised overall result was due to a number of cases transplanted after a long time delay. No patient transplanted beyond 3 years from the initial time of diagnosis of SAA achieved long-term marrow engraftment, and they all eventually succumbed. On univariate analysis, a longer time delay and hence a larger amount of blood products exposure, were highly significantly statistically associated with inferior marrow engraftment and patient survival. Other factors including age, iron status, infused cell dose and the conditioning protocol were not found to significantly affect engraftment and survival. Graft versus host disease was clinically mild or absent in most patients. This may be related to ethnicity or previous ATG exposure. In conclusion, early allogeneic BMT was a safe and effective treatment in our small series of patients with SAA failing IST.

Antithymocyte globulin treatment of retrovirus-induced feline erythroid aplasia: in vivo and in vitro studies

The Kawakami-Theilen strain of feline leukemia virus (FeLV-KT) was used experimentally to produce erythroid aplasia in cats. The in vivo effects of goat anti-feline-thymocyte globulin (ATG) on hematopoiesis were investigated in FeLV-negative normal and FeLV-positive anemic cats. Treatment was initiated in anemic cats between 4 and 6 weeks postinoculation (PI) when erythroid progenitors were reduced to 10% of normal levels. During the first 2 weeks of treatment, ATG significantly increased the numbers of erythroid precursors in bone marrow from 15 to 35% in anemic cats and from 28 to 43% in normal cats. ATG stimulated a twofold increase of CFU-E and a threefold increase of CFU-GM in normal cats between 2 and 4 weeks after initiation of treatment but had no effect on CFU-E or CFU-GM in anemic cats. The in vivo effects of ATG were transient despite weekly treatment. Cats treated with normal globulin were not significantly different from untreated anemic control cats. In vitro treatment of low density bone marrow mononuclear cells with ATG plus complement increased CFU-E and BFU-E of bone marrow from cats prior to inoculation but not from viremic cats. These results indicate that, although ATG stimulates erythropoiesis and granulopoiesis in normal cats, it does not reverse retrovirus-induced erythroid aplasia.

Aplastic anemia: analysis of two methods of treatment

Between 1981 and 1985, 27 patients with aplastic anemia have been treated by immunosuppression with antilymphocyte globulin and prednisolone or allogeneic bone marrow transplantation. Fifteen have undergone bone marrow transplantation and have an actuarial survival at 54 months of 65% +/- 12% (95% confidence limits). There have been four deaths from graft rejection, septicemia (two), and graft-versus-host disease. Twelve have received antilymphocyte globulin and have an actuarial survival at 56 months of 67% +/- 21%. Five of these now have a normal blood count and two have had good partial responses and are self supporting. Of the five non-responders, three survived, two with persistent aplasia and one after allogeneic bone marrow transplantation. Two are dead, one of hemorrhage and one after mismatched bone marrow transplantation. In this study antilymphocyte globulin produced survival equivalent to bone marrow transplantation although only 58% of patients had a response to the antilymphocyte globulin. The advantages and disadvantages of these two methods of treatment are discussed.