Immunosurveillance Essay Example | Topics and Well Written Essays - 1500 words

Immunosurveillance - Essay Example There is a third element in the research for investigating interactions between the immune system and neoplasia. This is that neoplasia deliberately develop certain defence mechanisms against the incumbent system in such a manner that they successfully evade punitive action (Chernock et al, Undated). This paper's purpose is to investigate what these evasive strategies may be and how they assist neoplasia to evade immune reaction. In the 1950s Lewis Thomas and Sir MacFarlane Burnet postulated the theory positing that effector cells of the immune system constantly patrol the body to actively identify and eradicate incipient tumour cells (Ichim, 2005). In the 1970, subsequent research found that T-cells may be implicated in this defensive mechanism (Ichim, 2005). This theory fell out of favour in the 1980s as research studies noted certain discrepancies in it but, in the 1990s, it was again revived because subsequent research studies noted that it was partially viable (Bhardwaj, 2007). It is observed that both the innate immune system - phagocytes, NK cells, NKT cells, cytokines, proteins, etc. - and the adaptive immune system - B- and T-cells, etc. - do fight neoplasia but, ultimately, it is observed for most spontaneous tumours that the overall immune system fails to entirely rid the organism of the cancerous cells. This is so as per three acknowledged phases to the immune response - 1) the elimination phase during which nascent tumourous cells are eliminated by the immune system; 2) the equilibrium phase when the tumour cells persist but are held in abeyance by the immune system; and 3) the escape phase when the tumour cells develop strategies to combat the immune system (Bhardwaj, 2007). This is the whole concept of 'immunoediting' and the last phase - the escape phase - is the one the paper is interested in because it is the one in which the neoplasia develop successful strategies in evading immune reaction. Evasive Strategies The evasive strategies adopted by neoplasia may be pre-existing or adaptive. Since such develop from healthy normal cells, some of the progenitor cells' evasive strategies pre-exist in them (Chernock et al, Undated). Pre-existing Strategies: Normal cells are incorporated by certain mechanisms that assist them in evading the body's own immune reactions. Such mechanisms may be self-tolerance, shielding from proper surveillance, antigen shedding, lymphocyte killing, secretion of immunosuppressive cytokines, lack of MHC2 expression, lack of co-stimulatory molecules and local secretion of prostaglandins and neuropeptides. These strategies are often sustained in neoplasm (Chernock et al, Undated). They ultimately, to a large extent, help the mutant cells maintain themselves with impunity in the organism's body. Adaptive Strategies: Nevertheless, such mutant cells are altered and have certain distinct proteins that differ from normal cells and these may be recognised by the immune system. To evade this eventuality such cells develop strategies that are not inherited from normal cells but are variants developed customarily by the mutant cells themselves as per requirements. Such adapted strategies may be up-regulation of the evasive tactics of healthy cells still existing in the mutants,