Differential Expression Of Cytokines In Aplastic Anemia

Aplastic anaemia(AA) is hemopoietic failure caused by several etiological factors, its pathogenesis is an attentive issue by far. A great deal of study indicates unbalance of immune mechanism plays an important role in occurrence of AA. T lymphatic cell and cytokines are important in immune regulation and correlated with pathogenesis of AA. Through detecting Interleukin(IL)-2,Interleukin (Il)-4,Interleukin (IL)-10,Interleukin (IL)-12,interferon(IFN)-gamma,tumour necrosis factor(TNF)-alpha of cytoplasm in peripheral blood cell as well as T lymphatic cell subset Th1 and Th2 by flow cytometry, 27 severe aplastic anaemia are involved and 20 blood donor are selected. It is discussed that the role of differential expression of cytokines and T lymphatic cell subsets in occurrence and development of AA The results show as followed: 1. The level of IFN-gamma in AA group is (2.3037±0.7439)%, being higher than those of normal controls (1.9760±0.5374)%. Over expression of IFN-gamma was observed in AA patients. IFN-gamma is a main factor in regulating T cell, B cell and NK cell, as well, enhance the function of mononuclear-phagocyte cell. It is reported that T cell in marrow of patients can produce hemopoietic inhibitory factor like IFN-gamma without stimulated in vitro and IFN-gamma is secreted by cytotoxic T cell culture in vitro. IFN-gamma play a role in inhibiting hemopoietic cell by arresting cell cycle and promoting apoptosis of CD34+cell by Fas signal pathway . Selleri proved that micro-endogenous IFN-gamma cause strong inhibiting effect, which indicates local low-dose IFN-gamma would lead to marrow inhibition. Our study coresponds with other reports. 2. The level of TNF-alpha was (8.4037±1.1182)%, being higher than those of normal controls(1.8550±0.431)%, the difference of TNF-alpha was statistically significant (p< 0.01). It indicates over-expression of TNF-alpha in AA patients enhance the number and function of inflammatory cell as lymphatic cell,mononuclear cell,neutrophilic granulocyte, also increase cytotoxicity of T lymphatic cell and NK cell. These indicate TNF-alpha as hemopoietic inhibitory factor play a inhibitory role in hemopoietic cell. The mechanism might be ①TNF-alpha induces to NO composition and aggravate hemopoietic failure in marrow. ②TNF-alpha activates phospholipase which produces free radical and peroxidase, they enter nuleus to injure DNA and affect proliferation and differentiation of stem cell, inhibit development of hemopoietic cell. It is reported that using immunosuppressive drugs can reduce expression level of IFN-gamma and TNF-alpha and prove that the role of TNF-alpha in immune regulation in AA in further. These results indicate that blood cells in patients with AA may possess high sensitivity to TNF-alpha. This in turn suggests that TNF-alpha affects hematopoiesis at an earlier stage in AA patients than in normal controls. 3. IL-12 induces help T cell to Th1 cell differentiation in early stage and promote proliferation of Th1 cell. Increase in number and hyperfunction of Th1 cell may be an important loop of marrow failure in AA. In the study, the level of IL-12 in AA is (3.1259±0.5789)%, being higher than those of normal controls (0.9850±0.3558)%. It is suggested that over-expression of IL-12 in patients relates to helplymphatic inhibitoryl in AA. IL-12 could inhibit helplymphatic cell by direct effect of cytotoxic T cell and inducing IFN-gamma. 4. IL-2 is produced by activated Th1 cell and NK cell, belonging to cytokine which can promote proliferation of T cell, strengthen activity of T cell and NK cell, promote antibody and IFN-gamma production and play akey role in maintain stable internal environment. Shinohara have reported that increase in IL-2 activity in AA induce to enhancing function of T cell and regulate T cell to secrete IFN-gamma to negatively control helplymphatics. This study showed that the level of IL-2 in AA is (2.7418±0.5051)%, being higher than those of normal controls (1.3250 ±0.4667)%. It indicated expression of IL-2 is participated in pathogenesis of AA. Some experiments in China have proved IL-2 super-expression related to cellular immunity unbalance in AA. 5. IL-10 is inhibitory cytokine produced by activated Th2 cell and mononuclear cell. IL-10 inhibit T cell secreting IFN-gamma and IL-2, as well as, inhibit activity of T cell and macrophage and from NK cell to releasing TNF-alpha by conjugating receptor to make cellular immunity. Our study indicate that the level of IL-10 in AA is (1.9333±0.6373)%, which have not significant difference with those of normal controls (2.1100±0.4191)%. Though IL-10 can mediate immune tolerance of T cell to antigen, have strong effect on immune tolerance and immune regulation, it indicated that expression of IL-10 closely related to occurrence and development of AA. While our study results are different from individual report, as its expression in cytoplasm is lower than that of in blood plasma, or its inhibition is interfered by other cytokines. The result is expected to discussion further. 6. IL-4 is mainly produced by activated Th2 cell, mastocyte and marrow stroma cell as well. Il-4 stimulates proliferation and differentiation of B cell as well as development of fibroblast and endothelial cell and regulates function of T cell, induce proliferation and activity of NK and LAK cell, inhibit activity of cytotoxic T cell. The study indicates that the level of IL-4 in AA is (1.9444±0.3786)%, which have not significant difference with normal control(2.0050±0.3348)%. Expression of IL-4 is approximately similar andit hint IL-4 is not closely related to pathogenesis of AA. 7. In the present, unbalance in cytokine network is thought as definite effect on pathogenesis of AA. In this study, the expression level of cytokine as IFN-gamma,IL-2,TNF-alpha,IL-12 in AA patients is higher than those of normal control. We analyze differential expression of the cytokine in our study indicate that only three index of TNF-alpha,IL-12,IL-2 are selected(p<0.01), Wilks'Lambda index is in turns 0.075,0.048,0.043. The equation formulated by TNF-alpha,IL-12 and IL-2 is Y=-9.084+0.909×TNF-alpha +1.158×IL-12+0.167×IL-2, the error rate is 0, which indicate that the equation is very stable and relate to AA. The three cytokines constitute mutual adjusting network. In the network, as upstream control factor in molecular level, TNF-alpha,IL-12,IL-2 are directly involved in pathogenesis of AA. Especially, TNF-alpha is more important(Wilks'Lambda index is 0.075). It affects helplymphatic function. Though over-expression of IFN-gamma is detected, IFN-gamma is still excluded, which hint IFN-gamma may be not primary increasing factor, but passive increasing factor as downstream control factor as TNF-alpha,IL-12,IL-2. However, micro-dose IFN-gamma enhance cytotoxicity of TNF-alpha. IL-10 can inhibit activated mononuclear/macrophage cell from producing TNF-alpha and directly or indirectly inhibit CD4+T cell from IL-2 and IFN-gamma production by inhibiting antigen processing cell. IL-10 as anti-helplymphatic inhibitory factor can inhibit cytokine of IFN-gamma and TNF-alpha. It is reported that IL-10 and IL-4 are not closely related to AA. 8. Activated T cell plays an important role in the pathogenesis of aplastic anemia (AA). Help T cells are divided into Th1 cells producing hematopoietic inhibitory cytokines like interferon-gamma and Th2 cells producing interleukin-4. We investigated the percentage of Th1,Th2...