Innate Immunity (17) Flashcards
3 lines of defense associated with the human body
Physical, Chemical, and Cellular
Types of Physical Defenses
Skin, Mucus Membrane, and Endothelia cells
- Epidermis- few pathogens can penetrate these layers, shredding of dead skin cells removes microorganisms, epidermal dendritic cells phagocytize pathogens
- Dermis- Collogen fibers help skin resist abrasions that could introduce microorganisms
- Chemical defenses of skin- salt inhibits growth of pathogens, lysozyme destroys cell wall of bacteria, defensins, and dermcidin’s
Role of Skin in Innate Immunity
Line the mouth, nose, lungs, and urinary and digestive tracts to provide another barrier against pathogens. Epithelial cells bound by tight junctions. Epithelial cells secrete mucus, which covers and protects the more fragile layers beneath and traps debris and matter including pathogens. Mucus also contains Antimicrobial Peptides
Role of Mucus Membranes
Tightly packed cells lining the urogenital tract, blood vessels, lymphatic vessels, and certain other tissues
Blood brain barrier protect the central nervous system (CNS), which consist of the brain and spinal cord
Role of Endothelia
Physically remove pathogens from the body, preventing them from taking up residence. EX: Eyelid, eyelashes, tear duct, shedding of skin, excretion of feces through intestinal peristalsis
Mechanical Defenses
contain the chemical mediator’s lysozyme and lactoferrin, both of which are capable of eliminating microbes that have found their way to the surface of the eyes. Lysozyme cleaves the bond between NAG and NAM in peptidoglycan, a component of the cell wall in bacteria. bacteria. Lactoferrin inhibits microbial growth by chemically binding and sequestering iron. This effectually starves many microbes that require iron for growth.
Role of Tears
urine flushes microbes out of the body during urination. Furthermore, the slight acidity of urine (the average pH is about 6) inhibits the growth of many microbes and potential pathogens in the urinary tract.
Role of the Urinary System
a special class of nonspecific cell-derived mediators with broad-spectrum antimicrobial properties. Some are produced routinely by the body, whereas others are primarily produced (or produced in greater quantities) in response to the presence of an invading pathogen. Defensins, Dermcidin, and Lysozyme
Antimicrobial Pepides
antimicrobial peptides which are encoded by the DCD gene in human being and often secreted by sweat gland cells to provide a broad-spectrum antibacterial activity against several pathogens.
Dermcidin
May be secreted or act inside the host cells; they combat microorganisms by damaging their plasma membranes
Defensins
AMP, which breaks down and digests the peptidoglycan in their cell walls
Lysozyme
soluble proteins that act as communication signals between cells
may be releases to stimulate production of chemical mediators or other cell functions (cell proliferation, cell differentiation, inhibition of cell division, apoptosis, and chemotaxis)
Cytokines
Same cell secretes and receives cytokine signal
Autocrine
Cytokine signal secreted to a nearby cell
Paracrine
Cytokine signal secreted to circulatory system; travels to distant cell
Endocrine
3 classes of Cytokines
Interleukins, Chemokines, and Interferons
produced only by leukocytes and only stimulate leukocytes
cytokines largely produced by immune system cells that help coordinate efforts against invading pathogens
Interleukins
chemotactic cytokines that recruit specific subsets of leukocytes to infections, damaged tissue, and sites of inflammation
Chemokines
cytokines released by cells that have been infected with a virus; stimulate antiviral responses in nearby cells as well as the cells secreting (viral replication)
Interferons
Complement System Activation (3 ways)
Classical pathway, Alternative pathway, and Lectin pathway
initiated by the spontaneous activation of the complement protein C3. The hydrolysis of C3 produces two products, C3a and C3b. When no invader microbes are present, C3b is very quickly degraded in a hydrolysis reaction using the water in the blood. However, if invading microbes are present, C3b attaches to the surface of these microbes. Once attached, C3b will recruit other complement proteins in a cascade
Alternative pathway
more efficient mechanism of activating the complement cascade, but it depends upon the production of antibodies by the specific adaptive immune defenses. To initiate pathway, a specific antibody must first bind to the pathogen to form an antibody-antigen complex. This activates the first protein in the complement cascade, the C1 complex. The C1 complex is a multipart protein complex, and each component participates in the full activation of the overall complex. Following recruitment and activation of the C1 complex, the remaining proteins are recruited and activated in a cascading sequence
Classical Pathway
similar to the classical pathway, but it is triggered by the binding of mannose-binding lectin, an acute-phase protein, to carbohydrates on the microbial surface. Like other acute-phase proteins, lectins are produced by liver cells and are commonly upregulated in response to inflammatory signals received by the body during an infection
Lectin Pathway
