Innate Immunity Flashcards
Two defense systems
-Nonspecific defense system (innate immunity)
-Specific defense system (adaptive immunity)
Immunity
Ability to resist or eliminate potentially harmful foreign invaders
Innate Immunity
-Physical barriers
-Chemical barriers
-Cellular defenses
First line of defense of innate immunity
Barrier defenses
Innate immunity
Protection from or resistance to infection by non-immune response mechanisms
Body coverings
-Intact skin (contains keratin - structural protein that helps form protective barrier)
-Mucous membrane (trap pathogens)
Chemicals produced by the body
-Acid in the stomach
-Fatty acids and secretion form tears, sweat, and oil glands are toxic to bacteria and fungi
Barrier defenses
-Trachea lined with ciliated cells and cells that secrete mucus
-Esophagus leads to stomach with a pH of 1-2 (acidic) which kills most pathogens
-Urinary tract has lower pH (acidic) and is flushed with urine
-Tear ducts with lysozymes
-Reproductive tract also has a lower pH (acidic)
Stomach mucosa
-Secretes hydrochloric acid
-Has protein-digesting enzymes (these kill many bacteria)
Barrier defenses
-Saliva and lacrimal fluid contains lysozyme (an enzyme that catalyzes the destruction of the cell walls of certain bacteria)
-Mucous traps microorganisms in digestive and respiratory pathways
Phagocytes
- Neutrophils : most abundant WBC
- Monocytes/macrophages
-Engulfs foreign material into a vacuole
-Enzymes from lysosomes digest the
material
Natural killer cells
-Can lyse and kill cancer cells
-Can destroy virus-infected cells
Immune cells that are granulocytes
Neutrophils, basophils, eosinophils
Chemical responses (#1)
- Kinins or chemokines (microbial peptides) are released by certain phagocytes
-These molecules increase circulation and capillary permeability
-Attract leukocytes to site of injury
-Affect nerve cells making area tender
Chemical responses (#2)
- Complement proteins (approx. 30 proteins) work by a number of different methods
-These proteins create pores in invading bacteria, causing water to rush in
Chemical responses (#3)
- Interferons secreted proteins made by virus-infected cells. Bind to healthy cell surfaces to inhibit virus bonding
Chemical responses (#4)
- Histamine is released by mast cells and basophil cells which are attracted to an injury site. When the skin is penetrated, cells are ruptured releasing chemical signals to attract the mast and basophil cells. These cells release histamine
Second line of defense
inflammation
Inflammation
-Increases capillary permeability. The area becomes swollen, red, temp increases from the increased blood flow
-Phagocytes leave the capillary bed because they are attracted to histamine and other signals
-Phagocytes clean up pathogens and cell debris
Homeostasis and inflammatory response
-Inflammation continues as long as the triggers (pathogens) are present
-When phagocytes complete their job by removing the pathogens, macrophages begin to secrete substances that: suppress inflammation, promote tissue repair
Fever
-Abnormally high body temp
-Hypothalamus heat regulation can be reset by pyrogens (response to pathogens proteins and secreted by WBCs)
-High temperatures inhibit the release of iron and zinc from liver and spleen needed by bacteria
-Fever also increases the speed of tissue repair
