Adaptive immune system I Flashcards
What are the 2 types of innate immune response?
- Cell mediated
- Humoral
Briefly describe the innate response to new infection and why it’s important
- Response to new infection fast
- Acts on pre-determined non-self signals
- Sometimes can be primed/trained for intense reactivation (innate memory)
What are the components of the cell mediated innate response?
- Phagocytes
- Natural killer cells (NK cells)
What are the components of the humoral response?
- Complement and pentraxins (CRP)
- Pattern receptors (soluble TLR- toll-like receptors, makes response quick)
- Enzymes (lysozyme)
- Cytokines releasing antimicrobials
- Binding proteins (Lactoferrin)
Briefly describe the adaptive response to new infections
- Slow
- Selects for specific signals and generates memory
Where are T and B cells made?
- Bone marrow with a randomly assigned antigen-binding specificity
- T and B cells can have the same specificity
What cells and molecules are involved in the innate immune response?
- Dendritic cell
- Mast cell
- Macrophage
- NK cell
- Complement protein (mark pathogens to be destroyed)
- Neutrophil - granulocyte
- Eosinophil - granulocyte
- Basophil - granulocyte
What cells and molecules are involved in the adaptive response?
- B cell
- Antibodies
- CD4+ T cell (T helper cell)
- CD8+ T cell (T cytotoxic cell)
Where are T lymphocytes developed?
Migrate to Thymus gland, become CD8+, CD4+ or are destroyed if strongly recognise self antigens (central tolerance)
Where are B lymphocytes developed?
- Bone marrow
- Developed and matured in bone marrow to express a single epitope antibody used as a receptor to bind to an antigen
What is T cell priming?
The activation and clonal expansion of a naive T cell on initial encounter with antigen on the surface of an antigen-presenting cell
Describe the endogenous pathway of T cell priming
- Endogenous antigen pathway leads to cytotoxic (CD8) T cell priming
- Antigen binds to APCs
- These cells are infected by the virus
- Viral proteins in the cytoplasm are detected and processed
- Viral antigens presented with MHC class I molecule on cell surface
- CD8+ cell recognises antigen, becomes cytotoxic, begins to make cytokines
- Cytotoxic T cell (CTL) proliferates making memory cells, and CTL cells looking for cells with presented antigen
- Infected cell destroyed by cytotoxic cell
Describe the exogenous pathway of T cell priming
- Exogenous pathway leads to T helper cell priming
- Antigen (pathogen) engulfed by dendritic cell or macrophage via phagocytosis
- Antigen processed into small peptides
- Antigen presented with MHC class II molecule on cell surface
- CD4 T helper cell recognises presented antigen
- CD4 Th cell becomes primed and can help with either B cell activation or macrophage activation
Describe antibody-antigen interaction
- Non covalent interactions
- Electrostatic, hydrophobic, van der Waals, Hydrogen bonds
- Depends on antibody binding site being exactly complementary sterically and chemically, with a site on the surface of the antigen
- A single antigen can have many possible binding sites (epitopes)
Describe the structure of antibodies
- Immunoglobulin + glycoprotein
- 2 identical antigen binding sites
- A hinge ‘H” region - flexible space between binding sites
- Protease cleavage generates large fragments called Fab (variable region, antigen binding) and Fc (constant region, crystallisable)
- 4 polypeptide chains help together by non-covalent interactions by disulphide crosslinks between cysteine
- 2 identical Heavy chains
- 2 light chains
- Carbohydrates help assembly and binding to cells
