Innate & Adaptive Immunity Flashcards
What cells are involved in the innate immune response to viral infection?
- Plasmacytoid dendritic cells (PDCs)
- Natural killer cells (NKs)
- Macrophages and Myeloid dendritic cells (MDCs)
How do innate immune cells influence adaptive response?
Innate cells are major drivers for the adaptive immune response, as their activity leads to production of inflammatory cytokines
How are T lymphocytes activated?
APCs present antigens to T-cells in stimulatory environment, which triggers T cells to secrete cytokines
How do dendritic cells initiate antibody production?
- DCs present antigens on the surface of MHCII molecules
- MHCII activates CD4+ cells which release cytokines
- cytokines activate B lymphocytes which differentiate into plasma cells
- plasma cells secrete IgM antibodies
What is the structure of antibodies?
- 2 heavy chains (4 domains) and 2 light chains (2 domains)
- chains are connected via disulphide bonds
- Fab region (top) binds antigens, contains variable regions which recognise epitopes
- Fc region works as biological activity mediation
How are antigens presented on cells?
- protein is taken up through endocytosis
- fuse with vesicles derived from Golgi apparatus which contain MHCII molecules which bind invariant chain
- once in fusion vesicle the invariant chain is released and the peptide can bind in groove of a-b chains of MHCII
- once peptide is bound it is transported to cell surface and peptide is presented to helper T cells
- Th cells carry CD4 which reacts with MHCII
Role of CD4 T-cells in antiviral immunity?
Th1: provide help to CD8 T cells, induce proliferation, recruit pro inflammatory macrophages, and can also directly eliminate infected cells
Th2: help B cells to produce antibodies
How are CTLs activated?
- MHCI binds CD8+ T cells, releasing cytokines
- cytokines released from Th cells are required for activation of cytotoxic T lymphocytes (CTLs)
- CTLs differentiate and start killing cells
How do CD8 cells eliminate infection?
- kill cells through release of perforin, granzymes and other cytolic proteins
- trigger death via TNFa or FasL
- produce soluble factors which cure the cell
What are the effector functions of antibodies ?
- bind pathogen leading to opsonisation
- after coating a pathogen, can be opsonised by APC and macrophages
- can bind toxins and neutralise them
- required for binding NK cells or eosinophils
- can activate complement
- can trigger mast cell degranulation
Properties of IgG?
- prototypic type
- 2 light chains, 2 heavy chains
- 2 binding sites
- bind phagocytes
Properties of IgM?
- required for immediate immune response and acts quickly
- are pentameters interlinked with J chain
- large, so cannot permeate barrier between mother and baby, so do not acquire these
Properties of IgA?
- a dimer
- important for immunity at mucosal surfaces
- secreted in tears, mucous, colostrum, saliva
Properties of IgE?
- antibody of allergy and antiparasitic activity
- Fc binds to mast cells and basophils
Properties of IgD?
- is a B cell receptor
