In Vitro And The Mixed Lymphocytes Culture,the Effect And Mechanism Of Antigen On Activation Lymphocytes

Background: Imbalance of immune response is a important reason of immune diseases and failure of organ transplantation. The holy goal for immune diseases and transplamation are how to induce immune tolerance of the immune system . At present , Immunosuppressants are the only protocol of choice besides several side effects. Apoptosis is a kind of common physiological and pathologic phenomenon in organ that is commonly viewed as a silent cell death without damage to adjacent tissues. it has been obvious for a long time that apoptosis plays a central role in fetal development and organogenesis, its significance in the immune system has been recognized only in recent years, but the effect of apoptosis on immunity is unclear. Some data have demonstrated that donor apoptotic cells can actively regulate immune system, too.Lymphocytes play an importantly role in the immune system. Apoptosis of mature T lymphocytes preserves peripheral homeostasis and tolerance by countering the profound changes in the number and types of T cells stimulated by diverse antigens, A balanced economy of cell production and destruction isimportant because the lymphocyte compartment has a limited capacity, Immune responses often involve the dramatic expansion of specifically reactive T cells.T cell apoptosis occurs in at least two major forms: antigen-driven and lymphokine withdrawal. These forms of death are controlled in response to local levels of IL-2 and antigen in a feedback mechanism termed propriocidal (AICD) regulation.Resting mature T-lymphocytes are activated when they are triggered via their antigen-specific Tcell receptor (TCR) molecule or the associated CD3 antigen. In contrast, preactivated T-cells can undergo activation-induced cell death (AICD) in response to the same signals. Active antigen-driven death is mediated by the expression of death cytokines such as FasL and TNF. These death cytokines engage specific receptors that assemble caspase-activating protein complexes.These signaling complexes tightly regulate cell death but are vulnerable to inherited defects. Passive lymphokine withdrawal death may result from the cytoplasmic activation of caspases that is regulated by mitochondria and the Bcl-2 protein.The human disease, Autoimmune Lymphoproliferative Syndrome (ALPS) is due to dominant-interfering mutations in the Fas/APO-1/CD95 receptor and other components of the death pathway. The study of ALPS patients reveals the necessity of apoptosis for preventing autoimmunity and allows the genetic investigation of apoptosis in humans. Immunological, cellular, and molecular evidence indicates that throughout the life of a T cell, apoptosis may be evoked in excessive, harmful, or useless clonotypes to preserve a healthy and balanced immune system.In conclusion, there are several lines of evidence that antigen- induced cell death contributes to the regulation of cellular immune responses as well as to the establishment of peripheral immune tolerance. Increased knowledge of the...