6.7 Response to infection Flashcards
What is the definition of an antigen
A substance which stimulates the production of an antibody when it gets in the body
Where antigens/markers found ?
Cell surface membranes or on bacteria cell walls.
What are the differences between self antigens and non self antigens
Self Non self
- Antigens are produced by organisms own body cells - Found on bacteria cell walls
- Are a type of MHC - Stimulates immune response
- Do not stimulate immune response - Result in the production of
antibodies by B Lymphocytes
What are the two types of phagocyte
Neutrophils
Macrophages
How are bacteria cells discovered in the blood
- Via opsonin recognising foreign chemicals on bacteria cell wall and tag them as foreign
What are the physical barriers to infection and how does each one work ?
- Skin : Tough physical barrier containing keratin
- Stomach acid : Which contains hydrochloric acid
- Gut bacteria : Competes for with pathogens for food and space
How does antigen presentation work?
- Enzymes in cell digest pathogens
- ## Cells then present the antigens from them on their MHCs on outer membrane
How does antigen presentation stimulate immune response ?
Antigens on MHCs are presented to the immune system
What are the two main stages of the humoral response ?
- T helper activation
- The effector stage
Explain T helper activation
- Pathogen engulfed by macrophage
- Macrophage uses digestive enzymes (lysosomes) to digest pathogen
- Pathogenic antigens displayed on MHCs
- Macrophage APC binds to T helper cells with complimentary receptors
- T helper cells become activated and divides to form T helper cells and T memory cells
Where are T helper cells formed and where do they mature ?
- Formed in bone marrow and matured in thymus gland
What triggers the division of T helper cells
- Production of cytokines
Explain the effector stage
- Pathogen binds to B lymphocyte with complimentary receptors
- B cell engulfs the antigen and digests it
- It then displays antigens on MHC to become the APC
- Activated T helper cell binds to B cell APC and produces cytokines
- This causes the B cell to divide (clonal selection) to form effector cells and memory cells
- Effector cells differentiate into plasma cells which produce antibodies, memory cells which can differentiate into plasma cells if reinfection occurs
What are some ways opsonisation can work ?
- Coat the pathogen in antibodies to make it easier for macrophages to engulf.
- Coat the pathogen in antibodies to make it harder to enter host cells.
Explain cell mediated response
- Pathogen invades body cell.
- Infected body cell displays the pathogenic antigens on MHCs, becoming the APC
- T killer cells bind to receptor on MHC.
- Cytokines from T helper cell causes killer cells to divide into killer cells and memory cells
- Other t killer cells bind to other APC’s, releasing chemicals causing the cell walls to lyse
