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    as in what do they bind to and how do they get activated on reinfection with the antigen? in particular memory t and b cells? many thanks
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    Hi, sorry you have not had a reply yet - I can only provide the brief points below - you might want to consult an immunology text in your uni library for more detail.

    1. Memory cells (in common with other lymphocytes) have a long lifespan, thus conferring prolonged retention of their antigen recognition properties.
    2. These cells are recirculated from tissues into the bloodstream, providing distribution throughout the body.
    3. A mechanism that activates memory cells is the binding of certain cytokines (e.g. IL-15 - interleukin-15) to the cell on re-exposure to specific antigen.

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    (Original post by jonjoshelvey21)
    as in what do they bind to and how do they get activated on reinfection with the antigen? in particular memory t and b cells? many thanks
    They get reactivated in the same way as they did during the primary infection. The pathogen/antigen is taken up by a dendritic cell or macrophage, where they process the pathogen/antigen and present a part of the antigen (the epitope) on their surface on MHC II molecules. Dendritic cells migrate to the regional lymph node, where they present the epitope/antigen to helper T cells. Helper T cells that have the T cell receptor (TCR) that recognises that antigen becomes activated, proliferate and differentiate into effector T cells and memory T cells. B cells are also antigen-presenting cells, and when they encounter their antigen, they phagocytose it and present it on MHC II molecules on their surface. When the corresponding helper T cell recognises the B cell presenting this antigen, the helper T-cell releases cytokines which, along with costimulatory molecules on the T cells, activates the B cell, causing it to proliferate, undergo class switching (from IgM to IgG) and affinity maturation (new antibodies have higher affinity than the old ones) and differentiate into plasma cells and memory B cells. This process is exactly the same for memory cells, the only difference is, is there is a greater number of memory cells than there were naive B and T cells, and memory B cells have high affinity IgG receptors on their surface, as opposed to the low affinity IgM receptors on the surface of naive B cells.
 
 
 
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