MHC class I molecules have peptides that bind to T cell receptors on cytotoxic T lymphocytes. These are found on the cell surface of almost all nucleated cells in the body and allow T cells to distinguish between “self” antigens and foreign antigens. This interaction also involves the binding of a CD8+ T cell surface glycoprotein to the MHC molecule (class I) (McDowall, n.d.). Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay. MHC class II molecules however display peptides recognized by helper T cells. Only specialized antigen-presenting cells express MHC class II molecules, which consist primarily of dendritic cells, macrophages, and B cells. Binding of helper T cells to MHC class II molecules also involves binding of a cell surface glycoprotein. CD4+ T cells. It is the difference between the CD8+ and CD4+ glycoprotein receptors that allows these two subgroups of T cells to be distinguished. When T cell receptors bind to antigens presented by MHC molecules, signal transduction occurs that induces a T cell response. Helper T cells Helper T cells (also known as CD4 T cells) are not directly involved in attacking pathogens or infected cells, however they are extremely important as they are required for almost all adaptive immune responses. Naïve T cells are activated by causing them to mature, proliferate, and coordinate immune responses by secreting cytokines that act on other immune cells. There are two main types of T helper cells, classified according to their cytokine secretion profiles, which determine their functions: type 1 (TH1) cells mainly secrete the cytokines interleukin (IL)-2 and interferon gamma (IFN- γ). They participate in cell-mediated immunity and activate macrophages, antibody production and cytotoxic T lymphocytes. They can also cause delayed-type hypersensitivity (DTH). Type 2 (TH2) cells secrete cytokines IL-4, IL-5, IL-10, and IL-13 that help B cells promote Ige antibody synthesis as well as activation of eosinophils, mast cells, and deactivation of macrophages . two cell types also differ in the type of immune response they coordinate. TH1 cells generate immune responses against intracellular pathogens such as bacteria and viruses while TH2 cells respond to extracellular pathogens such as helminths (Perkel, 2001). Helper T cells also bind to B cells and secrete lymphokines that activate B cells by stimulating them to differentiate into and produce plasma cells. Neutrophils and macrophages of the innate immune system serve as the first line of defense against invading pathogens. However, some of these pathogens cannot be recognized, so eliminating them requires a more specific approach by the adaptive immune system (Janeway, 2001). There are two divisions of acquired (adaptive) immunity, the humoral response which is mediated by antibodies and the cell-mediated response in which T lymphocytes play a central role. Antibodies are only effective against extracellular pathogens, once pathogens enter host cells they can evade the humoral immune system, which is when cell-mediated immunity acts to defend the body from intracellular pathogenic microorganisms (Silverthorn, 2015). a champion. Get a custom paper from our expert writers now. Get a Custom Assay T lymphocytes (T cells) originate in the bone marrow before migrating as thymocytes into the thymus where they mature, multiply, and differentiate (Khan, 2012). During their development, i.).