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Cell Recognition And The Immune System (Primary Immune System (1) When…
Cell Recognition And The Immune System
Defense Mechanisms
Non Specific- immediate response to ALL pathogens
Physical Barrier
Phagocytosis
Specific- slower responce to specific pathogens
Cell-Mediated Respnse, T Lymphocytes
Humoral Respnse - B Lymphocytes
Lymphocytes
Recognises own and foreign cells
Recognises proteins
Allows immune sys. to identify patogens and foreign cells, Toxins, abnormal body cells
Can reject tramsplanted organs
To minimise risk, transplants are normally matched as close as possible
Immunosuppressant drugs
Immune Response
1) Phagocytes Engulf Pathogens
Phagocyte recognises foreign antigens on pathogen
Phagocyte engulfs pathogen
Pathogen is now in a phagocytic vacuole in cytoplasm of phagocyte
Lysosome fuses with phagocytic vacuole and breaks down pathogen
Phagocyte presents pathogen's antigens, antigen presenting cell
2) Phagocytes Activate T-Cells
Receptor proteins on surface of t-cells bind to complementary sntigens presented by phagocytes, this activates the t-cell
Th cells activate and stimulate phagocytes and tc cells, kill foreign cells
Th cells can activate B-cells, secrete antibodies
3) T-Cells Activate B-Cells, / into Plasma Cells
B-Cells are covered with antibodies to form antigen-antibody complex
Once complex is formed activates the B-cell, CLONAL SELECTION
Activated B-cells divides into PLASMA CELLS
4) Plasma Cells Make Antibodies
Plasma cells are identical to B-cells, they're clones
Monoclonal antibodies are secreted, they bind to pathogens to form many antigen-antibody complexes
AGGLUTINATION - as antibodies have two binding sites two pathogens can bind to the at one time, pathogens become clumped t/g
Phagocytes can bind to antibodies and phagocytose many pathogens at once, leads to destruction of pathogens carrying antigen in the body
Primary Immune System
1) When antigen enters body for 1st time it activates immune response, PRIMARY RESPONSE
2) Slow, not many B-cells to make antibodies needed
3) Eventually body produces enough of right antibodies to overcome infection, person shows symptoms
4) Being exposed to antigen, T and B cells produce memory cells, remain in body for long time, memory T-cells remembers specific antigen + will recognise it second time round, memory B-cells record specific antibodies need to bind to antigen
5) Person is now immune
Secondary Immune System
1) If same pathogen enters body again, immune system will be quicker and stronger
2) Clonal selection is faster, memory B-cells activate + divide into plasma cells, produce right antibody to antigen, memory T-cells activate and divide into correct T-cells to kill cells carrying antigen
3) Often gets rid of pathogen before any symptoms show, IMMUNE