Innate Immunity Flashcards
What is a pathogen?
Biological agents capable of producing disease; include viruses, bacteria, and fungi.
What are the 3 lines of defense against pathogens?
1) Skin and mucous membranes
2) Innate defense mechanisms
3) Adaptive immunity
What is meant by innate defenses?
Defenses that guard equally against a broad range of pathogens.
Characteristics of Innate Immunity.
1) Local - wards off pathogen at the point of invasion with little effect anywhere else
2) Nonspecific - acts against broad spectrum
3) Lacks memory
What are the 3 types of innate defenses?
1) Protective cells
2) Protective proteins
3) Protective processes
How does skin function as an external barrier?
Makes it mechanically difficult for microorganisms to enter the body - toughness of keratin; too dry and nutrient-poor for microbial growth
What is the acid mantle?
Thin film of lactic and fatty acids from sweat and sebum that inhibits bacterial growth.
Where do you find mucous membranes?
Where “inside meets outside”; digestive, respiratory, urinary, and reproductive tracts
What is lysozyme?
An enzyme destroys bacterial cell walls.
Neutrophils
Can kill using phagocytosis and digestion; can kill by producing a cloud of bactericidal chemicals
What happens when lysosomes degranulate?
They discharge enzymes into tissue fluid causing a respiratory burst - creates a killing zone around neutrophil, destroying several bacteria
Eosinophils
Found especially in mucous membranes; it guards against parasites, allergens, and other pathogens - kills tapeworms and roundworms by producing superoxide, hydrogen peroxide, and toxic proteins.
Basophils
Secretes chemicals (leukotrienes, histamine, heparin) that aid the mobility and action of other leukocytes.
What do leukotrienes do?
Activate and attract neutrophils and eosinophils.
What does histamine do?
Increases blood flow (vasodilator)
What does heparin do?
Inhibits clot formation that would impede leukocyte mobility.
What are the three different types of lymphocytes?
T cells, B cells, Natural Killer cells
Monocytes
Emigrate from the blood into connective tissues and transform into macrophages
What are antimicrobial proteins?
Proteins that inhibit microbial reproduction and provide short-term, innate immunity to pathogenic bacteria and viruses; two families: interferons, complement system
What do interferons do?
Secreted by certain cells infected by viruses; Alert neighboring, activate second-messenger systems within, NK cells & macrophages
What is the complement system?
A group of 30 or more globular proteins that make powerful contributions to both innate immunity and adaptive immunity; float around in inactive form, activated by the presence of a pathogen
What are the 3 routes of complement activation?
Classical pathway, alternative pathway, lectin pathway.
Describe the classical pathway of classical activation.
1) Antigen-antibody complexes form on the pathogen surface
2) Reaction cascade (complement fixation)
3) C3 dissociates into C3a and C3b
Describe the alternative pathway of classical activation.
1) C3 dissociates into fragments C3a and C3b
2) C3b binds to pathogen surface
3) Reaction cascade and autocatalytic effect
4) C3 dissociates into C3a and C3b
Describe the lectin pathway of classical activation.
1) Lectin binds to carbohydrates in pathogen surface
2) Reaction cascade
3) C3 dissociates into C3a and C3b
Describe the course of a fever.
1) Infection and pyrogen secretion
2) Hypothalamic - thermostat is reset to higher set point
3) Onset-body temperature rises
4) Stadium - body temperature oscillates around new set point
5) Infection ends, set point returns to normal
6) Defervescence-body temperature returns to normal
Describe inflammation.
The process begins with the release of a variety of proinflammatory chemicals, such as histamin, from injured tissue, immune cells, and infectious organisms. This tiggers mobilization of body defenses, containment and destruction of pathogens, tissue cleanup and repair
What do cytokines do during inflammation?
Regulate inflammation and immunity - includes interferon, interleukins, tumor necrosis factor, chemotactic factors, and others
Describe the four cardinal signs of inflammation.
Heat: results from hyperemia
Redness: due to hyperemia, and extravasated RBCs in the tissue
Swelling (edema): due to increased fluid filtration from the capillaries
Pain: Direct injury to the nerves, pressure on the nerves from edema.
Describe neutrophil behavior in inflammation.
Chemical messengers are released by basophils, mast cells, blood plasma, and damaged tissue. These inflammatory chemicals stimulate leukocyte margination (adhesion to the blood vessel wall), diapedesis (crawling through gaps in the wall), chemotaxis (movement toward the source of the inflammatory chemicals), and phagocytosis (engulfing bacteria or other pathogens).
