chariizard
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I've tried almost everything to understand the immunology section of AS biology. I understand phagocytosis but everything onwards i'm still finding super difficult (cell-mediated and humoral response etc) AS is on thursday any help would be greatly appreciated!!
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Kozmo
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Try to think of it in a cyclical manner. Although this is not necessarily completely true (i.e it doesn't always occur in this order), remembering it in the following way helps it to stick in my head:

Phagocytosis:

  1. Phagocytes are attracted to chemical products of a pathogen.
  2. A phagocyte engulfs a pathogen, forming a phagosome (a phagocytic vacuole) around the pathogen.
  3. Lysosomes are attracted to and fuse to the phagosome, releasing lysozymes (digesting enzymes) into it and thus destroying the pathogen.
  4. The products of the hydrolysis of the pathogen are absorbed by the phagocyte and recycled. The antigens are presented on the phagocytes surface.

T-Cells:

  1. A T-Cell (T-lymphocyte) binds to an antigen presented on the surface of a pathogen using a specific, complementary receptor. This stimulates and activates the T-Cell.
  2. The T-Cell replicates (via mitosis) and forms T-Helper cells, Cytoxic T cells and T-Memory cells.
  3. Cytoxic T cells produce a chemical which helps destroy the pathogen (this is called perforin and destroys the cell wall, but you don't need to know this).
  4. T-Helper cells release chemicals (cytokines - but you don't need to know this) which activates B-Cells (the binding of B-Cells to antigens also does this)

B-Cells:

  1. Activated B-Cells (those which have binded to an antigen using an antibody on its surface to form an antigen-antibody complex) replicate themselves (clone) by mitosis. Plasma cells and B-Memory cells are formed as a result - these are identical to the parent cell as they were produced via mitosis.
  2. Plasma cells produce the monoclonal antibody which is complementary (due to its unique tertiary structure = variable region) to the antigen of the pathogen.
  3. Anitbodies bind to two antigens (and thus pathogens) at a time, and thus agglutinate (cause them to stick) the pathogens. This facilitates the action of phagocytes and allows them to destroyed more easily.

--> Memory cells stay in the blood and circulate, and record ('memorise') which antibody is specific to a pathogen and which antigen is specific to a pathogen. This enables a much quicker, more effective 'secondary response,' if one is re-infected with the same pathogen i.e they have built immunity.

The order is thus as follows (not really necessarily, but for memory's sake): Phagocytosis --> T-Cell action --> B-Cell action.

The first two steps (phagocytosis and the action of T-Cells) make up the cellular response = remember this as it involves phagocytes = the only step which doesn't have the word 'cell' in it, yet this one is called 'cellular' = this is not the real reasoning, just the way I recall it.

The last step, and thus the production and action of monoclonal antibodies through B cells is thus the humoral response.


Read over this a few times and try to recall it without looking. My above work is fairly condensed and spot on in knowledge for our level (as far as I'm aware).
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chariizard
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(Original post by Kozmo)
Try to think of it in a cyclical manner. Although this is not necessarily completely true (i.e it doesn't always occur in this order), remembering it in the following way helps it to stick in my head:

Phagocytosis:

  1. Phagocytes are attracted to chemical products of a pathogen.
  2. A phagocyte engulfs a pathogen, forming a phagosome (a phagocytic vacuole) around the pathogen.
  3. Lysosomes are attracted to and fuse to the phagosome, releasing lysozymes (digesting enzymes) into it and thus destroying the pathogen.
  4. The products of the hydrolysis of the pathogen are absorbed by the phagocyte and recycled. The antigens are presented on the phagocytes surface.

T-Cells:

  1. A T-Cell (T-lymphocyte) binds to an antigen presented on the surface of a pathogen using a specific, complementary receptor. This stimulates and activates the T-Cell.
  2. The T-Cell replicates (via mitosis) and forms T-Helper cells, Cytoxic T cells and T-Memory cells.
  3. Cytoxic T cells produce a chemical which helps destroy the pathogen (this is called perforin and destroys the cell wall, but you don't need to know this).
  4. T-Helper cells release chemicals (cytokines - but you don't need to know this) which activates B-Cells (the binding of B-Cells to antigens also does this)

B-Cells:

  1. Activated B-Cells (those which have binded to an antigen using an antibody on its surface to form an antigen-antibody complex) replicate themselves (clone) by mitosis. Plasma cells and B-Memory cells are formed as a result - these are identical to the parent cell as they were produced via mitosis.
  2. Plasma cells produce the monoclonal antibody which is complementary (due to its unique tertiary structure = variable region) to the antigen of the pathogen.
  3. Anitbodies bind to two antigens (and thus pathogens) at a time, and thus agglutinate (cause them to stick) the pathogens. This facilitates the action of phagocytes and allows them to destroyed more easily.

--> Memory cells stay in the blood and circulate, and record ('memorise' which antibody is specific to a pathogen and which antigen is specific to a pathogen. This enables a much quicker, more effective 'secondary response,' if one is re-infected with the same pathogen i.e they have built immunity.

The order is thus as follows (not really necessarily, but for memory's sake): Phagocytosis --> T-Cell action --> B-Cell action.

The first two steps (phagocytosis and the action of T-Cells) make up the cellular response = remember this as it involves phagocytes = the only step which doesn't have the word 'cell' in it, yet this one is called 'cellular' = this is not the real reasoning, just the way I recall it.

The last step, and thus the production and action of monoclonal antibodies through B cells is thus the humoral response.


Read over this a few times and try to recall it without looking. My above work is fairly condensed and spot on in knowledge for our level (as far as I'm aware).
Sorry i didn't reply but thank you this is really helpful !!
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