Immunity

• Antigen

  usully proteins present on the CSM of cells have specific 3d shapes/ tertiary structures act as markers, identifying self or non self cells foreign antigens are non-self antigens
• Phagocytosis

  Phagocyte attrated to a substance/recognising foreign antigen (Chemotaxis)

  Pathogen is engulfed

  Enclosed in a vacuole/vesicle/phagosome

  Vacuole fuses with a lysosome

  Lysosome contains hydrolytic enzymes

  Pathogen is digested/hydrolysed

  If antigen presenting cell e.g macrophage, display antigens on its CSM
• Cell mediated responses

  -uses t-cells for specific immune response

  Antigen presenting cell presents antigens on CSM

  Antigen is sepcific to complimentary receptor on t-cell which binds to antgen forming antigen-receptor complex

  Antigen receptor complex activates the t-cell
• What can be Antigen presenting cells

  -Phagocytes/macrophages

  -Transplant cells

  -Virally infected cells

  -Cancerous cells
• T-cell activation and differentiation

  Divides by mitosis then differentiates into one of 3:

  T-helper cells Th- secrete cytokines to stimulate phagocytes and activate b-cells

  Cytotoxic Tc- secrete cytotoxins to kill cancerous/virally infecte cells

  Memory T cells- provid elong-term immunity to the same specific antigen presented
• Humoural response

  In blood involving b-cells every b cell has its own uniqueley shaped antibody (specific antigen receptor) on CSM

  b cells also have signalling receptors on csm that can bind to cytokines releaed by th cells activated when csm

  -bound antibodies into contact with complimentary shaped antigens from pathogen or phagocyte displaying antigens and cytokines from Th cells, leading to clonal selection
• 2 Ways antibody works

  Agglutination- antibody can bind multiple pathogens together dure to flexible hinges- too large to enter host cell and is easier to be phagocytosed

  Neutralisation- when antobidies bind to antigens on pathogen and prevent bining to host cell so cannot enter host cell
• Active immunity

  immune system makes its own antobodies after antigen stimukation
• Passive immunty

  antibodies made by another organuism and passed to other organism e.g breast feeding or antivenoms
• How does HIV lead to AIDS

  -Loss of Th cells Th cells damaged when hiv exits cells by budding Infected th cells destroye by Tc cells

  -Both lead to loss of Th cells

  - less cytokines

  - less B-cell activation, less plasma cells and less antibodies produced
• HIV replication

  -HIV binds to TH by its receptors being complimentary to a protein on TH surface

  -HIV injects genetic info+enzymes

  -Reverse transcrptase turns viral RNA into viral DNA

  -Integrase inserts viral DNA into host genome

  -Host cell replicates viral DNA

  -In transcription, host cell produces viral mRNA

  -In translation host cell produces viral proteins

  -Viral proteins assemble and budd off of the Th cell

  - gaining a lipid coat of the host cell CSM
• Describe the roles of antibodies in producing a positive result in an ELISA test

  Enzyme Linked ImmunoSorbent Assay 1- first antibody binds to antigen 2-second antibody with enzyme attached is added 3- antibody attaches to antigen 4- substrate/ solution added- and colour changes
• What is an ELISA test

  Enzyme Linked Immumo Sorbent Assay Used to measure antibodies, antigens, proteins and glycoproteins e.g HIV infection, pregnancy tests and measurement of cytokines or sluble receptors
• What are Monoclonal Antobodies

  -produced from a single group of geneticaly identical B-ells -All identical in structure -Their specificity can be used in both diagnoses and treatment Issue: - produced inside animals - considered unethical
• Monoclonal Antibodies uses

  -cancer treatment- target cancer cells and deliver cytotoxic drugs -medical disgnoses- pregnancy tests and diagnosing diseases e.h hepatitis -separation- of molecules within a solution