Microbiology Chapter 15 EXAM

Innate nonspecific defenses

• rapid response to potential pathogens

• built-in mechanism; no memory capability

• responses are not perfect → damage

• not impenetrable → some pathogens can avoid

• lines 1 and 2 of defense

Specific adaptive defense

• responds to particular agents called antigens (viruses/bacteria)

• 3rd line of defense

Why is it that our bodies don’t often require the adaptive defenses to be activated, even though we are constantly exposed to potential infectious diseases?

the innate immune system works rapidly and is effective against a wide range of pathogens, reducing the need for the slower & more specific adaptive defense.

What is considered first line of defense? goal?

• physical & chemical methods

• goal = to prevent entry into body

Physical defenses

Skin -

• epidermis = layers of tightly packed cells; outermost layers continuously shed removing pathogens; few pathogens pass; dendritic cells

• dermis = thicker layer containing hair follicles, sweat glands, collagen that helps resist abrasions

Mucus membrane -

• epithelium = thin layer covering membranes; continual shedding; dendritic cells that phagocytize; goblet cells produce mucus & cilia move mucus

• deeper connective layer = supports epithelium

Chemical defenses

• antimicrobial peptides = disrupt microbial membranes, interrupt signaling, or act as chemotactic factors to recruit immune cells

• enzymes - lysozyme dissolves bacterial cell wall

• sebum - oil that keeps skin pliable & lowers pH

• secretions - saliva, tears, stomach acid, vomit, peristalsis

What is the 2nd line of defense?

cellular defenses → WBCs

Cellular defenses

Involve various cells (WBCs) that act to protect the body from pathogens.

• Phagocytes - engulf & digest pathogens

• Eosinophils - release toxins that kill parasites

• Natural Killer cells - identify & destroy cancerous cells through apoptosis

Inflammation

Nonspecific response to tissue damage caused by pathogens, heat, or cuts.

• Acute = quick, localized → dilation & increased permeability, migration of phagocytes, tissue repair

• Chronic = long-lasting, damage to tissues can cause disease

  • Ex: chickenpox rash

Fever

• body temp over 37 degrees C

• results when pyrogens trigger the hypothalamus to increase the body’s core temperature

• continues while pyrogens are present

• enhances interferons, inhibits microbial growth, enhance phagocytes

Molecular defenses

• Toll-like receptors = integral proteins produced by phagocytic cells that bind pathogen-associated molecular pathogens (anything but a eukaryote); bind microbial sugars & proteins

• Complement system = functions as chemoattractants and in opsonization (sticky tag) of pathogens for phagocytes + activates MAC → lysis of invading cell; C3; trigger inflammation & fever indirectly

Describe how mucus secretions in different parts of the body help in protecting against pathogenic microbes.

• Respiratory tract = trachea epithelium contains goblet cells that secrete mucus to trap cells and contains cilia that move the infected mucus away from the lungs

• Digestive tract = has epithelium that contains goblet cells (mucus) that trap invaders, mix with food, and move to excretion through peristalsis

Give examples of how mechanical defenses help to prevent infections

• Skin = tough; impermeable to most pathogens

• Mucus membranes = line various cavities & secrete mucus to trap pathogens

• Lacrimal apparatus = produces tears that wash pathogens away from the eyes; contain lysozyme that breaks bacterial cell wall

• Urination/defecation

What is the microbiome and what happens when it is disrupted or destroyed?

Microbiome = collection of microorganisms that live on and inside the human body without typically causing harm.

• Functions = consumption of nutrients, environment unfavorable for pathogens, prevent attachment, stimulate 2nd line of defense, antimicrobial compounds, vitamin & folic acid absorption

Disruption can lead to increased susceptibility to infection because there will be many nutrients for growth.

Antimicrobial peptides → functions & targets

Antimicrobial peptides (defensins) = present in skin, mucus membranes, & neutrophils. Triggered by sugar and protein molecules on the surface of microbes.

• Functions = membrane disruption, interruption of cellular processes, chemotactic activity, traps

• Targets a wide variety of microbes

What is the liquid part of blood and how much total blood volume does it account for?

Plasma - mostly water containing electrolytes, dissolved gases, nutrients, and proteins. Contains iron-binding compounds and complement proteins + antibodies.

• 55% of total blood volume

• when clotting factors are removed it is just considered serum

Cytokines

proteins that act as molecular messengers to facilitate various innate immune responses

• immune cells, cell death, etc

What are the classes of cytokines?

• Interleukins = produced by and stimulate a variety of cells, including leukocytes

• chemokines = specific in recruiting certain leukocytes to SITES OF INFECTION, TISSUE DAMAGE, and INFLAMMATION

• Interferons = group of immune signaling molecule important for viruses → induce apoptosis & antiviral defense

What are red blood cells called?

erythrocytes

What are white blood cells called?

leukocytes

Briefly describe how the different types of formed elements of the blood are formed from hematopoiesis.

Hematopoiesis = the process by which blood stem cells in the bone marrow produce various types of formed elements in the blood.

• erythrocytes = red blood cells that carry O2 and CO2

• platelets = involved in blood clotting

• leukocytes = involved in defending body against invaders; granulocytes & agranulocytes

Diapedesis

squeeze between the capillary endothelial cells out of the blood and attack invading microbes in tissues

Granulocytes

distinguished by the number of lobes in their nuclei & by the staining properties of their large granules

• basophils = stain blue; allergies; inflammation

• eosinophils = stain red/orange; phagocytic + diapedesis; PARASITES

• neutrophils = stain lilac; phagocytic + diapedesis + release toxins → extracellular fibers called NETS (trap bacteria) + oxygen radicals

Abbreviation for order of WBC in most to least

Never Let Monkeys Eat Bananas

Agranulocytes

cytoplasm appears uniform under microscope

• Monocytes = leave blood and mature into macrophages; phagocytic

• Lymphocytes = adaptive immunity; B & T cells; NK cells

Mast cells

• allergies & inflammation

• large granules containing inflammatory chemicals

Dendritic cells

• phagocytosis

• present antigens using MHC class I and II to T cells

• signal / activate T cells

Natural killer cells

kill via secreting toxins directly onto the surfaces of infected abnormal cells

• target recognition

Platelets

play a role in hemostasis (blood clotting) to prevent blood loss

• inflammation

How do phagocytes protect against invading microbes

They patrol throughout the body, engulfing and killing dead cells, debris, and microorganisms

What are the 6 stages of phagocytic elimination?

1. Chemotaxis → recognize invaders, release cytokines = phagocytes move towards infection

2. Adhesion → phagocytes attach to microbes with glycoproteins

3. Ingestion → pseudopod surrounds microbe & forms a food vesicle called a phagosome

4. Phagolysosome formation → phagosome and lysosomes fuze to create hydrolytic enzymes that break down bacteria

5. Microbial killing → use metabolic products to kill ingested microbes

6. Elimination = undigested remains are eliminated via exocytosis

Cardinal signs of inflammation

• Redness → vasodilation brings blood

• Warmth → same reason

• Swelling → increased permeability

• Pain → swelling puts pressure on nerve endings

• Loss of function

Is inflammation positive or negative?

Acute inflammation is positive as it is short-lived and allows for vasodilation, increased permeability, and phagocytic migration.

Chronic inflammation leads to tissue damage

What causes a fever? Should we treat them all?

Fever = pyrogens reset the hypothalamic thermostat and lead to increased body temp through shivering & vasoconstriction

No, because they can kill some microbes. But if high-grade 102-103 DEF seek help.

What are the different types of pyrogens?

• Exogenous pyrogens = bacteria or something has entered the body & releases toxins

• Sometimes phagocytes release pyrogens to tell brain to increase body temp

Role of gastroferritin

sequesters iron from being absorbed, making it unavailable for microbial use

• transferrin, etc