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How are phagocytosis, cell mediated immunity and humoral immunity related? Watch

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    Im taking biology OCR A AS, I do not understand the specific immune response at all I have several questions I could really do with some help with
    - how does a phagocyte bind to the antigen on the pathogen assisted by opsonins which tend to be antibodies if the antibodies have not been produced yet?

    - does cell mediated immunity trigger humoral immunity?

    - is phagocytosis not involved in humoral immunity being as B cells produce their own APC

    - how is the pathogen actually removed in humoral immunity? does the antibody go on to help phagocytosis?

    - what is the pathogen recognised the second time round for the correct antibodies to be produced

    - how do antibodies ever help destroy a pathogen if phagocytosis only partially digests it
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    (Original post by Gingeyy)
    Im taking biology OCR A AS, I do not understand the specific immune response at all I have several questions I could really do with some help with
    - how does a phagocyte bind to the antigen on the pathogen assisted by opsonins which tend to be antibodies if the antibodies have not been produced yet?

    - does cell mediated immunity trigger humoral immunity?

    - is phagocytosis not involved in humoral immunity being as B cells produce their own APC

    - how is the pathogen actually removed in humoral immunity? does the antibody go on to help phagocytosis?

    - what is the pathogen recognised the second time round for the correct antibodies to be produced

    - how do antibodies ever help destroy a pathogen if phagocytosis only partially digests it
    These are some pretty advanced level questions for A-level, but I'll answer them

    1) How does a phagocyte bind to the antigen on the pathogen assisted by opsonins which tend to be antibodies if the antibodies have not been produced yet?

    Phagocytes are non specific, they are part of the innate immune system, so they don't need antibodies to clear debris such as antigen. You're right in saying that opsonisation does greatly improve the efficiency of this process, however, there is a system called the complement system, which produces proteins that also act as opsonins. The complement system is part of the innate immune system and is partly stimulated by antigens, so it can opsonise antigen straight away.

    2) Does cell mediated immunity trigger humoral immunity?

    Most of the time it does, normally you get antigen presentation to T helper cells, which then activate B cells to release antibodies. However B cells can also be activated directly by antigen.

    3) Is phagocytosis not involved in humoral immunity being as B cells produce their own APC

    Not entirely sure what you mean by this, but just put it this way, humoral immunity is basically just referring to what antibodies do. So by that definition, phagocytosis is not part of humoral immunity. B cell phagocytosis of antigen is involved in activation of B cells, so it is kind of linked to stimulating a humoral response.

    4) How is the pathogen actually removed in humoral immunity? does the antibody go on to help phagocytosis?

    Antibodies have a number of jobs, they opsonise the pathogen to aid in phagocytosis (this only really works with bacteria, not viruses inside cells). They can also neutralise bacterial toxins and prevent bacteria from crossing membranes which is important. But they're also involved in cell-mediated cellular cytotoxicity, where the antibody binds to a cell and labels it for destruction by NK cells.

    5) What is the pathogen recognised the second time round for the correct antibodies to be produced?

    So the immune response is the same as in the primary infection, except it occurs much quicker and is much larger, this is because you have circulating memory T and B cells, which means less time is taken to find a T and B cell with matching TCRs and immunoglobulins and also the B cells undergo changes to increase their antibody binding affinity, so the immune response is much better the second time round because the cells are well practised you could say.

    6) How do antibodies ever help destroy a pathogen if phagocytosis only partially digests it?

    What do you mean by partially digests it? Phagocytes such as neutrophils contain many toxic granules involved in destroying the things they ingest. Partial digestion occurs to the antigen rather than the pathogen itself, this is because the antigen needs to be digested in a way that allows it to be presented on the cell surface.

    Hope that helps, they were some pretty deep questions haha
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    (Original post by AortaStudyMore)
    These are some pretty advanced level questions for A-level, but I'll answer them

    1) How does a phagocyte bind to the antigen on the pathogen assisted by opsonins which tend to be antibodies if the antibodies have not been produced yet?

    Phagocytes are non specific, they are part of the innate immune system, so they don't need antibodies to clear debris such as antigen. You're right in saying that opsonisation does greatly improve the efficiency of this process, however, there is a system called the complement system, which produces proteins that also act as opsonins. The complement system is part of the innate immune system and is partly stimulated by antigens, so it can opsonise antigen straight away.

    2) Does cell mediated immunity trigger humoral immunity?

    Most of the time it does, normally you get antigen presentation to T helper cells, which then activate B cells to release antibodies. However B cells can also be activated directly by antigen.

    3) Is phagocytosis not involved in humoral immunity being as B cells produce their own APC

    Not entirely sure what you mean by this, but just put it this way, humoral immunity is basically just referring to what antibodies do. So by that definition, phagocytosis is not part of humoral immunity. B cell phagocytosis of antigen is involved in activation of B cells, so it is kind of linked to stimulating a humoral response.

    4) How is the pathogen actually removed in humoral immunity? does the antibody go on to help phagocytosis?

    Antibodies have a number of jobs, they opsonise the pathogen to aid in phagocytosis (this only really works with bacteria, not viruses inside cells). They can also neutralise bacterial toxins and prevent bacteria from crossing membranes which is important. But they're also involved in cell-mediated cellular cytotoxicity, where the antibody binds to a cell and labels it for destruction by NK cells.

    5) What is the pathogen recognised the second time round for the correct antibodies to be produced?

    So the immune response is the same as in the primary infection, except it occurs much quicker and is much larger, this is because you have circulating memory T and B cells, which means less time is taken to find a T and B cell with matching TCRs and immunoglobulins and also the B cells undergo changes to increase their antibody binding affinity, so the immune response is much better the second time round because the cells are well practised you could say.

    6) How do antibodies ever help destroy a pathogen if phagocytosis only partially digests it?

    What do you mean by partially digests it? Phagocytes such as neutrophils contain many toxic granules involved in destroying the things they ingest. Partial digestion occurs to the antigen rather than the pathogen itself, this is because the antigen needs to be digested in a way that allows it to be presented on the cell surface.

    Hope that helps, they were some pretty deep questions haha
    That was VERY HELPFUL thank you! sorry about the deep questions, I have this problem where I think into things too much rather than just learning the content that I'm given and it really messes with me haha
 
 
 
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