Immunology Flashcards
State two ways pathogens cause harm
Viruses destroy cells by replicating inside the host
Bacteria produce toxins
Harm causing cells
Pathogens
Cells from other organisms of the same species
Abnormal body cells - cancer cells
Toxins secreted by pathogenic bacteria - snake venom
Antigen
Molecule (protein) that stimulates an immune response
Results in the production of a specific antibody
Antibody generator
Non self cells
Foreign cells or pathogens
Covered in specifically shaped antigens
Initiates an immune response to destroy the cell/pathogen
Phagocytes
White blood cells
Will engulf and digest non self cells
Phagocytosis
The processor engulfing and digesting a non self cell/pathogen
First line of defence
Tears
Mucus/Cilia
Skin
Scabs
Phagocytes
Eyelashes
Describe the process of non specific immunity
- Pathogen is engulfed by phagocyte
- Engulfed pathogen enters cytoplasm in a vesicle and his now a phagosome
- Lysosomes fuse with phagosome releasing hydrolytic digestive enzymes
- Lysosome enzymes hydrolyse the pathogen
- Waste materials released by exocytosis
- Antigens presented on the cell surface and phagocyte becomes an antigen presenting cell
Specific immunity
A specific response to a specific antigen on the surface of a cell that is non self
What it the primary response
Cell mediated immunity using T lymphocytes
Cellular response
- Phagocyte engulfs and hydrolyses the pathogen and presents the antigen on its cell surface
- T Helper cell with specific receptor molecule binds to presented antigen
- Once T Helper cell binds to activated antigen, it is activated
- T helper cell clones rapidly by mitosis
What is the advantage of having more T Helper cells
More cytokines to attract phagocytes to the area of infection
Role of T Helper cells
- Specific T Helper cells bind to antigen presenting cell
- Release cytokines that attract phagocytes to the area of infection
- Release cytokines that activate cytotoxic killer T cells
- Activates specific complimentary B cells
- Forms memory cells
Role of cytotoxic killer T cells
Locate and destroy infected body cells that present the correct antigen
2. Binds to the antigen presenting cell
3. Release perforin protein which creates holes in the membrane of the cell to destroy the APC
Humoral response
Involves the activation of B cells to produce antibodies. B cells are stimulated by the release of cytokines
B cell activation
A specific T helper cell with correct receptor binds to presented antigen and locates and activates specific complimentary B cell
The cytokine releases chemicals that signal the B cells to clone by mitosis
The B cells differentiate into plasma cells or memory cells.
Plasma cells - produce and secrete specific antibodies into the blood plasma
Memory cells - Remain in the body to rapidly reproduce in the case of pathogen re entering
Antibody
Protein made in response to foreign antigen
Antibodies structure
Quaternary structure
Four polypeptide chains
Y shaped
Antigen binding sites on top of the Y
Main body called constant region
Variable regions have different tertiary structure
Complimentary to one antigen
Disulphide bridges hold chains together
Antigen + antibody =
ANtigen - antibody complex
How do antibodies assist in the destruction of pathogens
Agglutination - when antibodies bind to antigens and clumps together
Opsonisation - marking pathogens so phagocytes recognise and destroy there pathogen more effectively
Lysis - bind to antigens, leading to the destruction of pathogens membrane
Anti-toxin - binds to toxins to prevent the molecules from binding to their complimentary receptors
Prevent pathogen replication
Memory cells
Not directly related to destroying the pathogen
Activated by cytotoxic killer T cells
Divide rapidly by mitosis
Secondary response
Secondary response
Rapid and extensive
Antigenic variability
The change in the antigen due to mutation
Makes it difficult to vaccinate against these pathogens
Passive immunity
No exposure to antigen
No production of memory cells
By mother or injection of antibodies
