Cancer immunity Cell surface proteins

A major function of the immune system is thought to be destruction of cancer cells. In this case altered cell surface carbohydrates or proteins elicit an antibody response with destruction of the offending cells. 

GSLs play crucial roles in functions of the nervous system and skin, cell growth and differentiation, infections, cancer, and immune response [1, 2, 12], Owing to their strategic position in membranes, they interact with toxins, bacteria, and viruses. They form membrane lipid rafts and present the attached carbohydrates as cell-surface receptors and, thus, serve as portals of entry for pathogens through carbohydrate-protein interactions [13]. For example, HIV entry is mediated by GalCer receptors of the host cells [14],... 

Some cell-surface receptors are attached to the plasma membrane by lipids that penetrate only into the outer leaflet of the bilayer. Posttranslational modification of proteins with GPI-lipids allows proteins such as folate receptor-2 (FOLR2) to attach to the cell surface and promote RME of the vitamin 5-methyltetrahydrofolate. Folate receptors are upregulated in certain cancers, and folate derivatives have been linked to drugs and molecular probes to treat and image certain tumors. The related GPI-linked receptor FcyRIIIB (CD16, 26.2 KDa, Fig. 1) is involved in the immune response. This receptor binds the invariant Fc region of immunoglobulin-G to promote RME of this... 

Major histocompatibility complex (MHC) proteins are essential components of the immune system (1). One speeific role is for them to bind and present cellularly derived peptides (-8-10 amino acids - MHC Class I peptides) at the cell surface. These peptides are subsequently challenged by cytolytic T-lymphocytes (CTL s) which are programmed to differentiate between self and exogenous peptides. T-cell recognition of these latter peptides initiates a response that ultimately results in cell lysis and death of the infected cell. Hence, structural characterization of such peptides could potentially result in the development of therapeutie treatments of a number of infectious disease states such as viral cancers, AIDS, and autoimmune disease. However, the task of sequencing such peptides is difficult since MHC class I proteins can bind and present 10,000-15,000 different cellularly derived peptides present at the sub-pieo-femtomole level (2,3). 

The cells of the innate system initially attack a pathogen, such as a virus, bacteria, or even a cancerous cell. They then present antigens from the pathogen on their surfaces via their MHC proteins. The acquired immunity cells then recognize the MHC/antigen complex, bind to it, and begin the involvement of the acquired immunity system. 

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