Biology Q&A Assignment

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Biology Q&A Assignment

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This is a Biology Q&A assignment answer according to the questions.

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1. Explain how “rare” antigen specific T cells can encounter a DC bearing their cognate antigen in a timely manner.

Over time, the immune system has developed to ensure that the rare antigen-specific T cells encounter occurs within the minimum amount of time possible. The encounter is initiated when the lymph node draining an inflamed tissue creates a highway that in turn recruits as many lymphocytes as possible. This is attainable through an increased vascularity that makes the HEVs to be more attractive and attract more migratory cells. The DCs gather around HEVs and screen the newly arriving lymphocytes. This encounter ensures that a large portion of cells will get a chance of interacting with the antigen-bound dendritic cells within its confines. Lymphocytes are motile cells while dendritic cells are more sessile but actively probe their local environment with their long dendrites. DCs can probe a large volume of lymph nodes relative to their own size thus increasing their rate of contact with mobile lymphocytes that may be moving away from them through the stromal network.

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