Chemical Mediators and Nonspecific Immunity Quiz

Chemical Mediators and Innate Nonspecific Immunity

• Chemical mediators are substances found in body fluids and tissues that inhibit microbial invaders.

• Chemical mediators may be endogenously or exogenously produced and can work alone or in conjunction to inhibit microbial infection.

• Sebum, an endogenous mediator produced by sebaceous glands, helps protect the skin from invading microbes, while oleic acid, an exogenously produced mediator, is created by resident microbes that degrade sebum.

• The digestive tract produces a variety of chemical mediators that inhibit or kill microbes, including lactoperoxidase enzymes and lysozyme found in saliva and mucus, and highly acidic gastric fluid in the stomach.

• Urine flushes microbes out of the body during urination, and the slight acidity of urine inhibits the growth of many microbes in the urinary tract.

• Lactate, an exogenously produced chemical mediator, inhibits microbial growth in the female reproductive system by lowering the pH in the vagina.

• Tears contain lysozyme and lactoferrin, which eliminate microbes on the surface of the eyes.

• Cerumen (earwax) exhibits antimicrobial properties due to the presence of fatty acids that lower the pH in the ears.

• The respiratory tract uses various chemical mediators in mucus, such as lysozyme, lactoferrin, and surfactant, to inhibit microbial infection.

• Antimicrobial peptides (AMPs) are nonspecific cell-derived mediators that have broad-spectrum antimicrobial properties and can induce cell damage in microorganisms.

• Acute-phase proteins, such as C-reactive protein and mannose-binding lectin, are produced in the liver and secreted into the blood in response to inflammatory molecules from the immune system.

• The complement system is a group of plasma protein mediators that can act as an innate nonspecific defense and is composed of more than 30 proteins that become activated when stimulated by factors such as the presence of microorganisms.Chemical Defenses and Mediators of Nonspecific Innate Immunity

• Chemokines recruit specific subsets of leukocytes to sites of infection and inflammation.

• Interferons are immune signaling molecules that inhibit viral replication and stimulate immune cells to attack virus-infected cells.

• Inflammation-eliciting mediators, including cytokines and histamine, contribute to inflammation and fever.

• Acute-phase proteins such as C-reactive protein and mannose-binding lectin act as opsonins, activating complement cascades through the lectin pathway.

• Mast cells and basophils release histamine, which promotes proinflammatory events such as bronchoconstriction and smooth muscle contraction.

• Leukotrienes are lipid-based proinflammatory mediators produced from the metabolism of arachidonic acid, which are more potent and longer lasting than histamine.

• Prostaglandins promote the inflammatory effects of kinins and histamines and can help to set the body temperature higher, leading to fever.

• Bradykinin contributes to edema by binding to receptors on cells in the capillary walls, causing the capillaries to dilate and become more permeable to fluids.

• Chemical defenses of nonspecific innate immunity include chemicals and enzymes in body fluids, such as sebum, lysozyme, and acid in stomach, urine, and vagina.

• Antimicrobial peptides, such as defensins and cathelicidin, kill bacteria by attacking membranes or interfering with cell functions.

• Plasma protein mediators, including acute-phase proteins and complement proteins, assist in trapping and killing bacteria and aid in phagocytosis.

• Chemical defenses and mediators of nonspecific innate immunity work together to expel pathogens from the body through mechanisms such as coughing, vomiting, and diarrhea.