Microbiology Lecture 13

Why is inflammation associated with the following physical signs: redness, warmth, swelling, pain?

due to the increased blood flow and vascular permeability

Define complement. Describe the three outcomes produced by the complement system: opsonization, inflammation, and cytolysis (MAC).

enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. 1) increases inflammation - complement enters the blood stream and binds to basophils. -> basophils then degranulates and releases histamine. -> thus inflammation amplifies. 2) amplifies phagocytosis - complement proteins leak out into the tissue & bind to bacterial cells. (called Opsonization - to coat) -> phagocytes can bind to complement protein via complement receptor. 3) cytolysis - there is a pore complement proteins create causing a hole to form in the membrane of a pathogen. MAC - membrane attack complex (particularly in G- bacteria) ->> hole forms by complement proteins ->> water enters cell rapidly causing the cell to burst, thus cytolysis = cell death.

Describe a situation when inflammation has a positive effect in the immune defense of the body, and a situation when inflammation has a negative (even deadly) effect.

inflammation is beneficial during a fever. cytokines are released which release histamine increasing redness/pain/swelling/edema/heat which is helpful to denature proteins and slow down viral replication. + destroy bacterial proteins. Inflammation is negative in a high fever. This can cause significant damage to cells in your body and can ultimately lead to organ failure or death due to inflammatory process not being able to kill off the pathogen.

Differentiate the following types of leukocytes: neutrophils, eosinophils, basophils/mast cells, lymphocytes (B and T), natural killer cells, monocytes, dendritic cells, and macrophages. Distinguish which ones differentiate from myeloid stem cells and which differentiate from lymphoid stem cells. Identify the appearance, relative abundance, and function of each leukocyte.

neutrophils - (60-70%) phagocytosis (3 lobes, cytoplasm stains pink/purp) eosinophils - (2-4%) releases granules, somewhat phagocytic. Lots of granules, stain pink in cytoplasm. basophils/mast cells - (.5-1%) Lots of purple granules + bilobed purple nuclei. granules full of histamine. triggers inflammation. Basophils are located in blood. Mast cells are located in tissues. B/T cells - huge circular nucleus that takes up most of the cytoplasm. natural killer cells - Large circular purple nucleus/granules in cytoplasm. granules contain 2 types: perforins + granzymes (toxic proteins) - destruction of foreign pathogens + also destroy cancer cells monocytes - (1-6%) very large bilobed nucleus (purp) cytoplasm stained light pink/purp. APC + phagocytosis dendritic cells - (1-6%) located in tissues. They look like dendrites. APC + phagocytosis macrophages - (1-6%) located in tissues. circular dark purp nucleus/jagged edges APC + phagocytosis

Explain how fever is caused and describe the positive and negative impacts of fever in fighting infection.

1) Il-1 (interleukin) secreted by phagocytes travels in blood to hypothalamus. 2) hypothalamus secretes prostagladin, which resets hypothalamic thermostat. (prostagladin = cytokine -> increases temp. and temp causes proteins to denature -> thus slows viral replication & destroy bacterial proteins) 3) never impulses cause shivering, higher metabolic rate, inhibition of sweating & vasoconstriction 4) these increase body temperature to the point set by hypothalamic thermostat.

Define inflammation and describe the steps in this process. Describe the role of the following cells: Macrophage, neutrophils, mast cells. Describe the role of the following chemicals: Histamine and cytokines.

1) cell injury or cell death -> releases inflammatory signals 2) specific white blood cells are activated. (cytokines release) e.g. mast cell will degranulate -> release histamine 3) vasodilation- blood vessels expand & become "leaky" (redness/pain/swelling/heat/edema). Selectin proteins form + attach to leukocytes. 4) Margination "leukocyte rolling" (sticking or rolling along to attach to selectin) 5) diapedesis leukocytes squeeze out of the blood vessel 6) phagocytosis

Describe the physical and chemical aspects of anatomical barriers to infection (first line of defense).

1) skin and oils, constant replacement of new skin cells. 2) cila/mucous lining cells of the respiratory tract "mucociliary escalator" 3) stomach acid 4) lysosomes (enzyme in saliva + tears): breaks PG, effective against G+ 5) nose hairs (any type of mucus layer)

Identify the three lines of defense in the human body. Which are innate defense (non-specific) and which are adaptive defenses (specific)?

1st line of defense = skin (physical + chemical barriers) (non-specific) innate immunity 2nd line of defense = leukocytes, fever response, inflammation, and complement (non-specific) innate immunity 3rd line of defense = B & T cells (specific immunity) adaptive immunity

Define antigen. Be able to identify examples of antigens.

Antigen - small molecules like proteins + polysaccharides Ex. lipopeptide, flagellin, and peptidoglycan

Define the role of antigens-presenting cells (APCs) in the immune response and explain the function of MHC markers to this process. Explain how antigen processing occurs. Identify which cells are as APCs?

Antigen presentation works by presenting the pathogens antigen on the cells surface via MHC. The antigen binds to the MHC and allows for the T cell to recognize the antigen and bind to the T cell. Function of the MHC is to display antigen on the macrophage. Macrophages, dendritic cells + B cells are APCs.

Describe what causes vasodilation, and the outcome of vasodilation.

Histamine causes vasodilation. and results in the blood vessels expanding and becoming "leaky"

What does MHC stand for? Explain where MHC are found, and their function. Which cells can make MHC class I, and which can make MHC class II?

MHC - Major Histocompatibility Complex found on all nucleated body cells (but not on RBCs) MHC I - body cells; function is to display peptide fragments of proteins from within the cell to cytotoxic T cells MHC II - macrophages, dendritic cells, and B cells; function is to present processed antigens

Define margination ("leukocyte rolling") and diapedesis.

Margination - sticking or rolling along to attach to selectin Diapedesis - leukocytes squeeze out of the blood vessel

Describe the function of phagocytes. Describe the main steps involved in phagocytosis. Be sure to include and understand the following terms: Pathogen, Antigen, Pathogen Recognition Receptors (P.R.R.s), lysosome, phagosome, and phagolysosome. How are ingested pathogens destroyed by the phagocyte?

Phagocytes func: they protect the body by ingesting harmful foreign particles. Phagocytosis: 1) leukocytes in the blood respond to chemical attractants released by pathogens and chemical signals from nearby injured cells 2) leukocytes squeeze between the cells of capillary wall as they follow the chemical signals to where they are most concentrated 3) within the damage tissue, neutrophils release chemicals that break apart pathogens. monocytes differentiate into macrophages. neutrophils and macrophages phagocytize pathogens and cellular debris. Pathogen - are bacteria, viruses, etc. that are composed of many antigens (smaller molecules like proteins +polysaccharides) Antigen - small molecules like proteins + polysaccharides Pathogen Recognition Receptors (PRRs) - proteins capable of recognizing molecules found on pathogens. Lysosome - is a enzyme in salvia + tears that can break peptidoglycan and effective against Gram+ Phagosome - vesicle formed around a particle engulfed by a phagocyte via phagocytosis. Phagolysosome - when a lysosome and a phagosome join together and the digestive enzymes from the lysosome bind to the pathogen. phagocytes aim to destroy pathogens by engulfing them and subjecting them to a battery of toxic chemicals inside a phagolysosome.