Microbiology Exam 1 (Study Guide 2)

Ch 14-16

What is the first line of defense mechanisms used by the body agaisnt pathogens?

Any barrier that blocks invasion at the portal of entry – innate/nonspecific

•       Physical barriers: skin, tears, coughing, sneezing

•       Chemical barriers: low pH, lysosome, digestive enzymes

•       Genetic barriers: resistance inherent in genetic makeup of host

Not considered a true immune response

What is the second line of defense used by the body against pathogens?

Recognition of foreign cells

Inflammatory response

Phagocytosis

Interferon

Complement

How does the body recognize foreign cells?

Protein receptors within the cell membrane of macrophages, called Toll-like receptors detect foreign molecules and signal the macrophage to produce chemicals to stimulate an immune response

What is the body’s inflammatory response?

Redness

Warmth

Swelling

Pain

Fever

What is phagocytosis?

The body surveys tissue compartments and discover microbes, particulate matter, and dead or injured cells, ingest and eliminate these materials, and extract immunogenic information (antigens) from foreign matter.

The phases: chemotaxis, ingestion, phagolysosome formation, destruction, and elimination.

What is an interferon?

Small protein produced by certain WBC and tissue cells in response to viruses, RNA, immune products, and various antigens. They induce changes in genetic expression and activate the development of WBCs.

What is the end product of the complement system regardless of inital pathway?

Membrane Attack Complex (MAC)

What are the stages of the complement system?

Initiation, amplification and cascade, polymerization, and membrane attack.

It activates inflammation, destroys cells, and participates in opsonization. 

What is the third line of defense mechanisms used to protect the body against pathogens?

This is acquired on an individual basis with exposure to foreign substances (infection or vaccine); it produces protective antibodies and creates memory cells that come into play if the microbe is encountered again.

Specific immunity - consists of B and T cell lymphocytes

What are pathogen-associated molecular patterns (PAMPs)?

Molecular marker on a pathogen that serve as a “red flag” to signal WBCs

What is a pattern recognition receptor (PRR)?

Special molecules found on WBCs that serve as “feelers” for sensing pathogens and recognizing them as foreign

What are the four major subdivisions of the immune system?

Mononuclear phagocyte system (MPS)

Extracellular fluid (ECF)

Bloodstream

Lymphatic system

What is the mononuclear phagocyte system (MPS)?

Connective tissue fibers that interconnects other cells and meshes with the connective tissue network surrounding organsW

Why is the MPS critical to the immune system?

It allows phagocytic WBC’s to move within and between tissues

What is the difference between serum and plasma?

plasma contains clotting factors while serum does not

Which cells differentiate from the myeloid stem cell?

RBC (from erythroblasts)

Platelets (from megakaryocytes)

Mast cells, Neutrophils, Basophils, Eosinophils (from myeloblasts)

Macrophage, Dendritic cell (from monocytes)

What cells differentiate from the lymphoid stem cell?

T and B cells (from lymphocytes)

NK cells

Which are the first immune cells to defend against infection?

Neutrophils

What is the primary function of the neutrophil?

phagocytosisW

What is the function of cytoplasmic granules?

They carry digestive enzymes that degrade the phagocytosed material

What do eosinophil granules target primarily?

They contain enzymes that are released to destroy eukaryotic pathogensIn

In what cases would eosinophils be elevated?

Infections involving parasitic worms (helminthes)

Inflammation

Allergy

What is the least numerous WBC?

Basophils

What chemical mediators do basophils release?

Histamine and heparin

How do the chemical mediators released by basophils affect the body?

Causes vasodilation in response to injury and help prevent clotting

They are involved with inflammation, allergic reactions and asthma

What differentiates a mast cell from a basophil?

Are larger and have more granules

Widely distributed, non-mobile, bound to connective tissue

Round nucleus

Which WBC is the key to the third line (specific) immune response?

Lymphocytes

Where do B and T lymphocytes mature?

B - bone marrow

T - thymus

Which type of lymphocyte provides humoral immunity?

B-cells

How do B-cells fight bacterial infections?

B-cells produce antibodies that cause the destruction of extracellular microorganisms and prevent the spread of infection to nearby issues

What is another name for humoral immunity?

Antibody-mediated immunity

What do monocytes differentiate into?

Macrophages and dendritic cells

What is the role of a macrophage?

They are the only cells large enough to clear pus, cellular debris, dead neutrophils, and damaged tissue from the site of an inflammatory reaction

Histiocytes: a macrophage that migrates to tissues and remains there

Ex. Alveolar macrophages, Kupffer cells in the liver, Langerhans cells in the skin, Macrophages in the spleen, lymph nodes, kidneys, bone and brain

What is the role of a dendritic cell?

Process foreign substances and prepare them for reactions with selected lymphocytes

Can remain nomadic or take up residence in a specific organ

Concentrated in skin and the linings of mucous membranes

What type of immunity are Natural Killer (NK) cells involved with?

Innate/ Non-specific

Why are NK cells considered to be apart of third line defense?

They do not display specificity or involve immunologic memory

Does NK activation involve immunologic memory?

They do not require activation in order to kill cells that are missing “self” markers

What is lymph?

A plasma-like liquid formed when blood components move out of blood vessels into extracellular spaces

Made up of water, dissolved salts and proteins

What is the function of lymph?

Provides an auxiliary route for return of extracellular fluid to the circulatory system

It acts as a drain off system for the inflammatory response. 

Renders surveillance, recognition, and protection against foreign material through the use of lymphocytes, phagocytes and antibodies

What direction is the movement of lymph?

Towards the heart

Vessels have one way valves

What are primary lymphoid organs?

Sites of lymphocyte maturation - thymus and bone marrowW

What are secondary lymphoid organs?

Circulatory based locations - spleen, lymph nodes, mucosal associated lymphoid tissue (MALT)

What are the actions of the second like of defense?

Recognition

Inflammation

Phagocytosis

Interferon

Complement

Explain the recognition stage of the second line of defense.

Protein receptors within cell membrane of macrophages (Toll-like Receptors: major sub-family of pattern recognition receptor PRPs) detect foreign molecules and signal the macrophage to produce chemicals to stimulate an immune response

Explain the inflammation stage of the second line of defense.

Blood vessels briefly vasoconstriction - blood clots and mast cells release chemokines and cytokines into the injured area

Nearby blood vessels dilate - increase blood flow, increased vascular permeability, increased leakage of fluid forms exudate (mass of cells and fluid) 

Collection of fluid - edema/swelling; infiltration by neutrophils and formation of pus 

Macrophages, lymphocytes, and fibroblasts migrate in - initiate immune response and repair of injury; scar and loss of normal tissue

Why is fever an important component of inflammation?

Inhibits multiplication of temperature-sensitive microorganisms

Impedes nutrition of bacteria by reducing the available iron

Increased hepcidin during inflammation leads to a decrease in serum iron levels

Increases metabolism and stimulates immune reactions and protective physiological processes

Explain the phagocytosis stage of the second line of defense.

Survey tissue compartments and discover microbes, particulate matter, and dead or injured cell

Ingest and eliminate these materials

Extract immunogenic information (antigens) from foreign matter

Explain the interferon stage of the second line of defense.

Produced in response to  viruses, RNA, immune products and various antigens

Bind to cell surfaces and induce changes in genetic expression

Activate the development of WBCs

Explain the complement stage of the second line of defense.

Consists of a group of serum proteins that activates inflammation, destroys cells and participates in opsonization

What is dispedesis?

WBCs migrating out of blood vessels and entering the tissue

What circulating substances cause fever?

Exogenous pyrogens - products of infectious agents

Endogenous pyrogens - liberated by monocytes, neutrophils, and macrophages during phagocytosis (ex. IL-1 and TNF)

How does MAC affect the cell membrane?

Contains enzymes that punctures small pores through the membrane, leading to cell lysis

What molecules are required to stimulate acquired specific immunity?

Produced by T and B cells

B cells produce memory cells (antibodies) in response to specific antigens and respond rapidly on the subsequent exposure

What two features characterize acquired immunity?

Natural - normal life experiences; exposure or secretions from mother to newborn

Artificial - acquired through medical procedure; vaccines and immune serums

Which cells have CD4 receptors?

Helper T cells

Which cells have CD8 receptors?

Cytotoxic T cells

What is cell-mediated immunity?

T-cells act directly against antigen and foreign cells when presented in association with an MHC carrier

Where are Class I MHC genes located and what cells to they present to?

Located on virtually all cell surfaces of the body that contain nuclei

Present to CD8 receptors

Where are Class II MHC genes located and what cells to they present to?

Located on cells with regulatory receptors (macrophages, dendritic cells, B cells)

Present to CD4 receptors

Which part of the immunoglobulin forms a binding site for the antigen?

Variable region

Describe where the heavy chains of an immunoglobulin are located.

They form a Y and are located in between the light chains (middle)

Contain constant regions (towards bottom) and variable region (towards top of Y shape)

What is an antigen?

A molecule that binds to components of the immune response and has the potential of invoking an immune response; is a specific type of pathogen

What is an epitope?

A molecular fragment of the antigen that serves as the primary signal to lymphocytes that the molecule is foreign; is also called antigenic determinant

What is a haptens?

A small foreign molecules that are too small by themselves to elicit an immune response

Not immunogenic unless attached to a large carrier.

When bound to a large carrier molecule, it serves as an epitope and stimulates a specific response

What is an allergen?

An antigen that evokes an allergic reaction

What is an autoantigen?

A molecule on self tissues for which tolerance is inadequate - accounts for some autoimmune diseases; can be mistaken as foreign

What is an alloantigen?

A cell surface marker and molecule that occurs in some members of the same species but not in others

Responsible for incompatibilities that can occur in blood transfusion or organ grafting rejection

What is a superantigen?

A potent T cell stimulator that provokes an overwhelming response and massive release of cytokines

Toxic shock syndrome

What is opsonization?

The process of coating microorganisms or other particles with specific antibodies so they are more readily recognized by macrophages

What is neutralization?

Antibodies fill surface receptors on a virus or the active site on a microbial enzyme to prevent it from attaching to their targets

What is agglutination?

Antibody aggregation; cross-linking cells or particles into large clumps renders microbes immobile and increases the speed with which they are phagocytized

What is complement fixation?

Activation of the pathway can result in the specific rupturing of cells and some viruses

What is precipitation?

Aggregation of free antigen molecules increases the speed they are phagocytized

What are the classes of immunoglobulins?

IgG - most prevalent

IgM - first synthesized

IgD - triggers B cell activation

IgA - defends mucosal surfaces

IgE - allergic responses and parasitic infections

Which immunoglobulins can cross the placenta?

IgG

Which immunoglobulin is involved in allergic and parasitic infections?

IgE

Which immunoglobulin is the first to be synthesized following an antigen encounter?

IgM

What is an anamnestic response?

Second contact with the same antigen immune response produces a more rapid, stronger response due to memory cells

Secondary response

What happens when T cells are exposed to superantigens?

Provoke overwhelming immune responses by large numbers of T cells

• Massive Release of cytokines

• Blood vessel damage

• Toxic shock

• Multiorgan damage

What is natural immunity?

Acquired through normal life experiences

Individual recovers from measles and develops immunity or infant receives antibodies through breast milk

What is artificial immunity?

Acquired through medical procedures

Vaccines and immune serums

What is active immunity?

Results when a person is challenged with antigen that stimulates production of antibodies

Creates memory, takes time, and long lasting

What is passive immunity?

When antibodies produced by the immune system of another human are donated to an individual

Does not create memory, acts immediately, and short term 

What type of immunity is developed when an individual recovers from measles or mumps and develops immunity?

Natural active

What type of immunity is developed when an infant receives antibodies through breast milk?

Natural passive

What type of immunity is developed after receiving a vaccination?

Artificial active

What type of immunity is developed when an individual is treated for rabies?

Artificial passive

What is a live attenuated vaccine?

Contain live virus particles or bacterial cell

Who should not receive live attenuated vaccines?

Not suitable for people with compromised immune systems - the vaccine strain could replicate too much and cause extensive, serious infection

What are examples of live attenuated vaccines?

MMR, chickenpox, yellow fever, bacterial TB, typhoid (oral)

What is an inactivated vaccine?

Contains whole bacterial cells or virus particles that have been killed or inactivated but does not destroy the antigenicity

What are examples of inactivated vaccines?

Hepatitis A, Influenza shot, Polio shot, Rabies, Typhoid (shot)

Which type of vaccination requires booster shots?

Inactivated - the microbe does not multiply

What is a viral vector vaccination?

utilizes low-pathogenic viruses that produce some of the same proteins as the disease-causing virus

use a modified version of a different virus to deliver protection

What are examples of viral vector vaccines?

Ebola, COVID

What is a subunit/acellular vaccine?

made from a piece of the pathogen, not the whole organism, and does not contain a live pathogen 

bacterial cell parts (acellular) or viruses (subunit)

What are examples of subunit vaccines?

Hepatitis B, HPV, Shingles

What are examples of acellular vaccines?

Pneumococcal pneumonia, Meningitis

What is a toxoid vaccine?

Consists of a purified fragment of bacterial exotoxin that has been inactivated

These vaccines elicit the production of antitoxins that can neutralize the natural toxin

Typically used for boosters in teens and adults

What are examples of toxoid vaccines?

Diphtheria, Tetanus