Innate immunity Flashcards
What are the 3 phases of response to initial infection and what are their timescales?
- Innate immunity: 0-4 hours
- Early induced response: 4-96 hours
- Adaptive immune response: >96 hours
What happens in 0-4 hours of infection?
- Innate immunity
- Recognition of infection by nonspecific effectors
- Removal of the infectious agent
What happens in 4-96 hours of infection?
- Early induced response
- Recruitment of effect cells
- Recognition and activation of effector cells
- Removal of infectious agent
What happens after 96 hours of infection?
- Adaptive immune response?
- Transport of antigen to lymphoid organs
- Recognition by naive B and T cells • Clonal expansion of effector cells
- Removal of infectious agent
What are the mechanical barriers to infection?
- Tight junctions between cells prevent access
- Air and fluid flow across the epithelium
- Movement of mucus by cilia
What are the chemical barriers to infection?
- Fatty acids on the skin
- Enzymes: lysozyme in saliva, sweat and tears
- Low pH in stomach
- Antibacterial peptides: defensins (skin and gut) and cryptidins (gut)
what are the microbiological barriers to infection?
- normal flora compete for nutrients and attachment (biofilms)
- Normal flora produce antibacterial substances (colicins)
What types of cells ingest micro-organisms once across the epithelial barrier?
- Mononuclear phagocytes
- Macrophages
What receptors recognise microorganisms for ingestion?
- Mannose receptor
- Glucan receptor
- Scavenger receptor
- CD14 (LPS)
- CD11v/CD18 (CR3)
Describe the environment of a phagosome
- pH of 3-4
- Toxic oxygen derived products: superoxide, hydrogen peroxide, hydroxyl radical
- Toxic nitrogen oxides: nitric oxide
- Peptides: defensins and other cationic proteins
- Enzymes: lysozyme, acid hydrolases
- Competitors: lactoferrin, vitamin B12 binding protein
What are the two pathways for bone marrow relating to the immune response?
Myeloid:
- Polymorphonuclear leukocytes
- neutrophils, basophils, eosinophils
Common lymphoid progenitor:
- B cells
- T cells
What are the effects of IFN alpha and beta?
- Induce resistance to viral replication in all cells
- Increases MHC class 1 expression and antigen presentation in all cells
- Activation of NK cells to kill virus infected cells
Why are natural killer cells important at the start of the immune response?
- Not specific
- Don’t require a lengthy clonal expansion of T cells in lymph nodes
What dictates if a natural killer cell is active?
- Balance between signals
- A positive signal to kill can be overridden by a negative signal by MHC molecules (inhibitory)
What is the complement system?
A cascade of serum proteins in the bloodstream
What is this cell and what is its role?
Macrophage
- Phagocytic cell
- Circulates in the blood
- Differentiates into macrophages in tissues
What is this cell and what is its role?
Macrophage
- Phagocytic cell
- Activation of T cells
- Inititates immune response
What is this cell and what is its role?
Neutrophil
- Phagocytic cell (rapidly phagocytoses then dies)
- Most numerous white blood cell
- Important in innate immunity
What is this cell and what is its role?
Eosinophil
- Killing of antibodies, coated in parasites
- Releases contents:
- histamine
- Peroxidases
- RNases and DNases
- Lipases
- Plasminogen
- Major basic protein
What is this cell and what is its role?
Basophil
- Granulocyte
- 0.1% of all white blood cells
- Secretes histamine, proteoglycans, leucotrienes
What is this cell and what is its role?
Mast cell
- Release number of substances that effect vascular systems e.g. histamine
- IgE mediated triggering allergies
