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Immunity (Humeral Immunity (This type of immunity involves B-cells, plasma…
Immunity
Humeral Immunity
This type of immunity involves B-cells, plasma cells and antibodies.
- B-cells are activated by a complementary antigen binding to an antibody on its surface. Helper T-cells also need to secrete cytokines in order for the B-cell to activate. This process is called clonal selection.
- The activated B-cells divide by mitosis, into cloned cells, and then differentiate into plasma cells and memory cells.
- They secrete loads of antibodies that are specific to the antigen that binded to the B-cell. These are called monoclonal antibodies.
- These antibodies bind to complementary antigens.
- Memory B-cells stay in the blood and allow a secondary response when the same pathogen enters the body for the second time.
Phagocytosis
- A phagocyte recognizes the foreign antigens on a pathogen.
- The cytoplasm of the phagocyte moves around the pathogen, therefore, engulfing it.
- The pathogen is now contained in the phagocytic vacuole.
- A lysosomes is fuses with the vacuole allowing the lyzosymes to hydrolyse the pathogen.
- The phagocyte presents the antigens of the pathogen on its cell-surface membrane to activate other immune system cells. It is acting as an antigen-presenting cell.
Cell Mediated Immunity
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- T-cells are specific to one antigen. and have a receptor with a complementary binding site for the specific antigen.
- This T-cell binds to an antigen on an infected cell or an antigen on an antigen-presenting cell.
- This activates the T-cell and it then divides by mitosis to form a clone. This clone differentiates into helper, memory or cytotoxic T-cells.
- Cytotoxic T-cells destroy cells directly, with a chemical called perforin.
Memory T-cells remain in the body and bring about a secondary response when the same pathogen enters the body for the second time.
Helper T-cells stimulate more phagocytosis, more cytotoxic T-cells and stimulate B-cells.
Other
Antibodies are a quaternary structure of and are made up of four polypeptide chains, linked by disulphide bonds.
Antibodies are made up of two light strands and two heavy strands, each made up of a constant group and a heavy group. The constant group is the same on all antibodies, however, the variable group is what makes the antibodies specific.
T-cells are made in the bone marrow and are matured in the thymus. When a cell is matured, it means that it is that cell permanently, e.g. once matured, a T-cell can't turn into a B-cell.
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