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    Also how exactly does the secondary immune response work?
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    (Original post by Jennifer50)
    Also how exactly does the secondary immune response work?
    Antigen presenting cells such as macrophages and dendritic cells engulf and digest the offending pathogen and present a portion of the antigen (the eptitope) on their plasma membrane on proteins known as type 2 major histocompatability complexes (MHC II). Helper T cells that have receptors which are complementary to the offending pathogen's antigens bind to the MHC II which activates them. Remember that if this is a secondary immune response, the number of helper T cells that are specific to the antigens (CD4+ cells) are likely to be elevated. These Helper T cells then release cytokines which activate other memory Helper T cells which in turn proliferate release more cytokines and also produce more memory T cells. These cytokines also activate memory B cells which will produce antibodies that are complementary to the antigen. These memory B cells then proliferate and differentiate into plasma cells, which then begin to produce antibodies, and more memory B cells. These antibodies can destroy pathogens in a number of ways: they can cause opsonisation, which recruit complement proteins which may cause lysis of the pathogen or enhance phagocytosis of the pathogen by binding to receptors on macrophages; precipitation of the pathogens; lysis of the pathogens; agglutination of the pathogens. The cytokines released also activate memory cytotoxic T cells, causing them to proliferate and differentiate into more memory T cells and effector cytotoxic T cells which bind to MHC class I on the plasma membrane of cells infected with viruses or bacteria and secrete perforins into the infected cell causing small pores to form in the plasma membrane of the infected cell causing it to lyse. With each subsequent exposure to the pathogen (or more specifically, the antigens) the body increases the number of memory B cells, memory Helper T cells and memory cytotoxic/killer T cells causing the secondary immune response to be much quicker and more intense and as such, the infection is usually cleared before symptoms appear.
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    So what exactly do t memory cells do? Can they activate the b memory cell?
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    (Original post by Jennifer50)
    So what exactly do t memory cells do? Can they activate the b memory cell?
    T-cells helps activate the B-cells. When the antibody on the surface of a B-cell meets a complementary shaped antigen it binds to it, this alongside the substances released by the helper t cells activates the B-cell. This is called clonal selection. The activated B-cell divides into plasma cells.
 
 
 
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