The Research Of Immunological Mechanisms In The Pathogenesis Of Aplastic Anemia

Aplastic Anemia (AA) is a heterogeneous disease characterized by failure of bone marrow hematopoiesis resulting in varying degrees of pancytopenia with a markedly hypocellular bone marrow. Clinically, patients with with AA may present with anemia, bleeding and serious infection. Despite the exact cuases of AA are unknown, the disease may result from the accumulated effects of multiple noxious exposures of plurpotential stem cells. Potential mechanisms responsible for acquired AA include induced defects in hematopoietic stem cells, failure of the bone marrow microenvironment which impaired production or release of hematopoietic growth factors, and cellular or humoral immune suppression of the marrow. The introduction of immunosuppression therapies such as antithymoctye globulin, antilymphocyte globulin, and cyclosporine A in the treatment of AA has improved the prognosis. Some of 70% patients recovered following immunosuppression suggestion that aplasia may be the an immune-mediated effect. T lymphocyte mediated suppression has been considered the most important in the development of AA. Further study T cells, especially abnormal activated T cells, were not only a useful marker to understand the pathegenesis of AA, but may have great implication on clinical application.Nowadays, more and more researchers have noticed that the disfunction of T cells play an important part in the pathogenesis of apastic anemia. The abnormal activated lymphocytes are the center part of aplastic anemia. We have successfully made the autoimmunity aplastic anemia mouse model. We can make further study of the pathogenesis of aplastic anemia on the mouse model. In our study, we observed and studied the role of T cells in the pathogenesis of plastic anemia, the influence of immunosuppressive intervention on the haematogenesis both in vivo and in vitro. As a result, our study is helpful to illuminate the effection of immuno- disfunction on the pathogenesis of apastic anemia, find new immunotherapy ways. And it may help us to make better clinic diagnoses, treatment and prognosis judgement.1. Male parent lymphocytes inhibit the colony formation of F1 hematopoietic cells in vitro.Hematopoietic cells from normal F1 mouse, lymphocytes from male parent mouse, we co-cultured these cells in certain proportion. Counting the number of CFU-E and CFU-G, we estimate the influence of lymphocytes on the hematopoietic cells. The results show that: When the number of lymphocytes is equal to the hematopoietic cells, comparing with the control group, there is no significant difference(p>0.05) in the number of CFU-E and CFU-G. When the number of lymphocytes is ten times of hematopoietic cells, comparing with the control group, there is a significant reduction (p<0.05) in the number of CFU-E and CFU-G. When the number of lymphocytes is fifty times of hematopoietic cells, no CFU-E or CFU-G can be observed. The larger the number of lymphocytes the smaller the number of CFU-E and CFU-G. We added different doses of CyA into the culture system, and observed their effection. The results show that: the dose from 100 ng/ml to 250 ng/ml can all increase the number of CFU-E and CFU-G, compared with the control group (p<0.05). There is no significant difference(p>0.05) between the 150ng/ml group and the 200ng/ml group. And no significant difference(p>0.05) between the100ng/ml group and the 250ng/ml group too. The number of CFU-E and CFU-G is larger in the 150ng/ml group than the 100ng/ml group(p<0.05) and 250ng/ml group(p<0.05). The number of CFU-E and CFU-G is larger in the 200ng/ml group than the 100ng/ml group(p<0.05) and 250ng/ml group(p<0.05). The results suggested that CyA can reverse the destruction of lymphocytes. And different concentration may have different results. It proved that suppressing T cell function can promote the recovery of haematogenesis function. The effection of male parent lymphocytes on F1 hematopoietic cells is a kind of immunosuppressive action that mediated by lymphocytes.2. Distribution of infused lymphocytes in the AA model mouse.The lymphocytes are tagged with CFDA-SE and injected in vein into the F1 mouse. When the F1 mouses are pancytopenia, we sacrificed the mouse. The frozen sections of lung, heart, liver, spleen, intestines, kidney and bone were observed under fluoroscope. At the same time, we examined the bone marrow and made the pathological section of bone, lung, liver and intestine. The bone marrow smears proved that the mouse is AA. The pathological section proved that there is no GVHD in the mouse. We can observed fluorocells in bone marrow, lung, kidney, spleen and liver. We counted the number of fluorocells of ten slides. There are more fluorocells in lung and bone marrow than in other organs. But the number of fluorocells in bone marrow are far small then the cells we infused into the mouse. So we consider that the infused lymphoctes trigged some mechanism, which induce the abnormal activation of lymphoctyes that aim directly at auto-hematopoietic cells. It finally caused the bone marrow failure of the mouse. This result is coincidence with our part one result. This model proved that the actived lymphocytes and typeâ… c ytokines play an important role in the lymphocyte infusion - induced bone marrow failure. We infer that the T cells of receptive mouse are universally in an activated state by the stimulation of the infusion lymphocytes. Those activated T cells secrete typeâ… cytokines. These result in the bone marrow failure of the receptive mouse.