chapter 14

first line of defense against infections, non-specific (doesn’t target a specific pathogen), defense against viruses, bacteria, fungi, immediate response to pathogen, built in and has no “memory”

physical/mechanical defenses, chemical defenses, cellular defenses

tight junctions, gap junctions, desmosomes

the dead cells of epidermis are covered with keratin. These form tight, dense layer of protein on the surface of the skin, the keratin makes the skin tough and resists breakdown by bacterial enzymes, fats on the skin create a dry, salty, and acidic environment that inhibits the growth of microbes

mucous membrane consists of a layer of epithelial cells held by tight junctions, the cells secrete mucus, which covers and protects the cell layers and trap debris and microbes, mucus secretions also contain antimicrobial peptides, in human trachea, cilia push mucus away from lungs, with trapped debris or microorganisms, up to the esophagus and away from the lungs

shedding of skin cells, expulsion of mucus via the mucociliary escalator, excretion of feces, secretion of urine and tears. Urine washes out transient microorganisms, the eyelashes and eyelids prevent dust and airborne microorganism from getting into the eye. Blinking washes away debris, the microbiota in gut/skin compete for nutrients preventing pathogen attachment and infection

sebaceous glands in the dermis secrete oily sebum, the sebum blocks bacteria from invading tissue, the bacterium propionibacterium acnes secrete lipase enzymes, degrade sebum, and use it as a food source, this creates an acidic environment on the skin surface that is in hospitable to many pathogens, saliva has lactoperoxidase enzymes, the mucus in the esophagus contains antibacterial enzyme lysozyme, in the stomach, acidic gastric fluid kills most microbes, the intestines have pancreatic and intestinal enzymes, antibacterial peptides, bile produced in the liver, and cells that produce lysozyme

a group of 30 plasma proteins (C1-C9) that circulate in blood, these proteins are activated by the presence of microorganisms, complement proteins are part of innate immunity because they are always found in the blood and tissue fluids, and can be activated quickly, when activated, these molecules form the membrane attack complex (MAC), a ring structure which perforates the cell membrane of pathogens, causing them to burst

opsonization (coat the pathogen), inflammation, chemotaxis (chemo attachment for neutrophils and WBC), cytolysis (MAC, membrane attack complex; works only on gram negative)

antimicrobial peptides (AMPs) secreted by cells have antimicrobial properties, AMPs damage the microorganism membrane, or interfere with cell-wall synthesis, a family of AMPs called defensins are produced by epithelial cells throughout the body and by macrophages and neutrophils, bacteria ins are secreted by microbiota in the gastrointestinal tract, acute-phase proteins produced in the liver and secreted into the blood in response to inflammatory molecules (activate complement, remove iron, coat bacteria)

proteins that act as communication signals between cells, stimulate production of chemical mediators, stimulate cell functions: cell proliferation, cell differentiation, inhibition of cell division, apoptosis, and chemotaxis, three important class of cytokines are the interleukins (stimulate leukocytes), chemokines (recruit leukocytes), interferons (defense against viruses)

innate capacity to recognize and differentiate any foreign material

agranulocytes- unlobed, rounded nucleus, granulocytes- lobed nucleus

neutrophils, basophils, eosinophils

destroy bacteria, migrate through blood vessels to areas of infection, where they kill bacteria, release defensins and hydrolytic enzymes by phagocytosis, degranulation: release toxic molecules in affected tissue that kill bacteria, as neutrophils fight an infection, leukocytes, cellular debris, and bacteria build up creating drainage

granulocytes that protect against Protozoa and helminths, they also play a role in allergic reactions

the only white blood cells circulating around your body that’s granules contain histamine. During an allergic reaction, histamine is responsible for many of the typical symptoms of allergies, like a runny nose or sneezing

cancer cells and virus-infected cells do not have the normal amount of MHC1 on their surface, NK cells recognizes cells with low to no MHC1 and kill the abnormal cells by releasing cytotoxic granules that contain perforin and granzymes. They can also induce apoptosis in target cells