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Discuss the key differences between MHC class 1 and MHC class 2 antigen presentation and the differential roles of T helper cells (CD4+ T-cells) and cytotoxic T-cells (CD8+ T-cells). Include in your answer a description of the different types of T helper cells (HINT: discuss Th1, Th2 and Th17 cells).

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Major histocompatibility complexes (MHCs) are a group of proteins that play crucial roles in the immune system by presenting antigens to T-cells. MHCs are divided into two classes, MHC class 1 and MHC class 2.

MHC class 1 antigens are presented mainly on the surface of cells that are infected with viruses or cancerous. Antigens presented on MHC class 1 molecules are recognized by cytotoxic T cells (CD8+ T cells) which respond by attacking and killing the infected cell.

MHC class 2 antigens on the other hand are presented exclusively on antigen-presenting cells (APCs). APCs present antigens to T helper cells (CD4+ T cells) which help the body recognize the pathogen or antigen and respond appropriately.

T helper cells are a type of immune cell that play a crucial role in the body’s immune response. There are three main types of T helper cells: Th1, Th2 and Th17. Th1 cells help the body fight off viruses, bacteria and fungi by secreting cytokines that activate macrophages and activate cytotoxic T cells. Th2 cells help the body fight parasites and allergens by secreting cytokines that activate B-cells to produce antibodies. Th17 cells also help the body fight bacterial and fungal infections by secreting cytokines that activate neutrophils and phagocytes.

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