Basics
What is the basic aspects of innate immunity?
First line of defense
Acts within hours/days of infection
Provides broad protection
Activates acquired immunity
What are the types of barriers for innate immunity
Physical barriers
Physiological barriers
cells
How is the skin and stomach a physiological barrier?
Sebum from sebaceous gland
= lactic acids and fatty acids (skin pH b/w 3 & 5)
= acne causing bacteria mobilize sebum
what are the two main opsonins?
C3b of the complement system
antibodies - specific to a pathogen
How do mast cells provide innate immunity
Induce vasodilation/diapedesis
signaling via histamine/eicosinoids
What are the cells that detect danger
Macrophages, neutrophils, Dendritic cells,
What are the physiological barriers of innate immunity
Body temperature
Skin and stomach pH
Antimicrobial peptides/enzymes
Interferons
Complement
Acute phase proteins
How are antimicrobial peptides/enzymes a physiological barrier?
Present in saliva, tears, mucus secretions (lung, gut, repro tract)
defensins, lysozyme
kill bacteria on membrane surface
What is chemotaxis
Process by which leukocytes follow chemical gradient of chemotactic molecules to site of infection
How do Polymorphonuclear nutrophils provide innate immunity
What are the secreated regulators and effectors
Regulators = Cytokines
effectors = Antimicrobial peptides, mucus
What is the complement cascade - Alternative/Lectin pathway
a whole series/family of proteins that function better & are present in ECF (work together to kill bacteria either directly or by enhancing phagocytosis
1 - alternative pathway - a protein that is always present in ECF & blood - hydrolyzes and sticks to cells
2 - classical pathway - proteins come together to punch holes in the surface to kill it
3 - lectin pathway
Alternative pathways and lectin pathways of complement activation are part of the innate immune system
The classical pathway of complement activation is activated by antibodies and therefore part of the acquired immune system
How are interferons a physiological barrier?
Secreted by virally infected cells and induce non-viral state in neighbouring cells
what are the chemotactic agents
C3a - peptide, Slowly diffuse away and make its way to a local capillary (defer immune cells to the site) = cells have receptors for C3a and use it to go up the concentration gradient of C3a, the higher the concentration the closer to the site where they're needed
Bacterial components
Chemokines/ecosinoids
How do macrophages/dendritic cells provide innate immunity
Phagocytic, bactericidal
inflammation signaling by secreted chemokines, cytokines, and eicosanoids
Antigen presenting cells - directing acquired immunity
What are the physical barriers of innate immunity?
Skin - keratinized physical barrier (pretty strong)
Epithelial cells/tight junctions (proteins that reach from one cell to another to hold them together)
Cilia (lining of the trachea) - physically expel -pathogens entrapped in mucus
Specialized secretions/cells - saliva, tears (wash away pathogens) and mucus secretions (lung, intestine, repro system = entrapment of physical barrier to epithelium)
What is phagocytosis?
Internalization and killing of pathogens
How is complement a physiological barrier?
Activated by innate and acquired arms of immunity
Cascade whereby serum proteins are activated leading to opsonization, chemotaxis, and killing of bacteria
What are the cells for innate immunity
Epithelial cells
Mast cells
polymorphonuclear neutrophils
macrophages/dendritic cells
natural killer cells
How do natural killer cells provide innate immunity
Cytotoxic, nonphagocytic
Tumour and viral surveillance
Mechanisms not well understood
Where do pathogens enter the most? why?
Lungs
GI tract
Repro tract
These are most susceptible to penetration due to being non-keratinized
What is opsinization?
Coating pathogens to promote phagocytosis
How are acute phase proteins a physiological barrier?
Increase markedly in serum during infection
C-reactive protein, serum amyloid A, haptoglobin, Fibrinogen
How do epithelial cells provide innate immunity
Physical defense
inflammation signaling with chemokines
How is danger detected?
Microbiota-associated molecular patterns (MAMPs) - molecular structures/motifs that are conserved within a class of microbes = bacteria, virus, fungi, protozoa
= molecules uniquely synthesized in the microbial world - not by multi cellular higher level organisms
= not so unique to pathogens
Pattern recognition receptors - receptor families that bind MAMPs and initiate inflammation