Innate Immunity - Binder Flashcards
What does a pathogen have to do to cause an infection (first step)?
They must adhere to the epithelium at the infection site.
What are some innate barriers to infection?
- Tight junctions between epithelial cells.
- Chemical secretions and mucins to prevent adherence
- Cilia
- Normal Flora
Describe the recognition-response paradigm in immunity.
The response of the immune system, both innate and adaptive arms rely on the ability of the immune cells to recognize pathogens.
What is a pathogen-associate molecular pattern (PAMP)?
PAMPs are conserved features of pathogen groups that serve as recognition sites for innate immune cells. These patterns are absent or shielded in the host to prevent recognition of self.
What is a Pathogen Recognition Receptor?
PRRs bind PAMPs to initiate a response. Response can be release of cytokines, complement, phagocytosis, etc. Receptors are present on macrophages, neutrophils, DCs, can be secreted, or can be intracellular.
What are the cellular elements of the innate immune system?
- Macrophages
- Dendritic Cells
- NK Cells
- Eosinophils
- Basophils
- Neutrophils
- Mast Cells
Where are macrophages and DCs found and what do they do?
Macrophages and DCs mature from monocytes and migrate to the tissues where they stay. Upon pathogen-pattern recognition, they will destroy pathogens without need for adaptive immunity and present antigens for T-cell recognition.
Where are neutrophils located?
Neutrophils are resident to the blood and only enter the tissues upon infection.
Describe the general phagocytic scheme.
Pattern recognition of pathogen by cell-surface receptors (mannose, scavenger, LPS (CD14) etc.) results in phagocytosis and initiation of inflammation and cytokine release. Pathogen is degraded and presented on MHC-II for T-cell activation.
Describe respiratory burst of macrophages.
Increase in oxygen consumption by macrophages. Oxygen will be converted to superoxide and H2O2 as a chemical toxin to pathogens or to form NO, a vasodilator and immune signaling molecule.
What are defensins?
A diverse group of small cationic antimicrobial peptides. They can assist with phagocytosis and form aggregates to disrupt pathogen membranes.
What are the effector mechanisms of innate immune cells?
- Phagocytosis
- Cytokine release
- Complement
- Respiratory burst
- Defensins
Describe the complement system
Soluble molecules circulating in blood that recognize and bind to pathogens and aid in opsonization and form membrane attack complexes.
PRR: Mannose-binding lectin (MBL)
Free protein in the blood that recognize certain carbohydrates specific to pathogens (by spacing). They opsonize pathogens and activate complement.
PRR: Macrophage Mannose Receptor (MMR)
Cell surface receptor of macrophages (CD206) that recognizes patterns similar to MBLs and acts directly as a phagocytic receptor.