Immune System A&P II

Lymphedema

swelling as a result of a build up of lymph

Diapedesis

when a leukocyte leaves the blood vessel and travels to infected tissue

AMP

antimicrobial peptide such as defensin that destroy germs a lot of the time by punching holes in the cell membranes

Opsonization

antibodies or other proteins (complement) mark the pathogen for death 

PAMP

pathogen-associated molecular patterns; antigens located on pathogens that reveal them as foreign to the immune system

ROS

reactive oxygen species; kills the invader but could also damage your own cells resulting in immunopathology

What are the functions of the lymphatic system

maintain fluid balance and filter fluid and help immune system identify and destroy germs 

How can the lymphatic system help a doctor diagnose an infection

when there is a infection, WBCs in the lymph nodes can increase, causing swollen lymph nodes

How does the lymphatic system distribute fluid around the body? In other words, it is not connected to the circulatory system proper, so the heart cannot push lymph around the body. How then does it move?

muscular pump and gravity. moves as the body moves

An infectious agent enters your body after cutting your finger. Describe the innate immune responses put into place to intercept and destroy the infectious agent

skin is the primary defense. past the skin is mucus and chemicals. then phagocytosis

What are some behavioral responses to systemic infection and how are they beneficial

wanting to sleep, get warm

Why is fever beneficial in the long run

slows germ growth rate

What is a differential WBC count and what does it tell us

tells us the amount of each leukocyte in the blood which can help determine if there is an infection and if so what kind of infection

What characteristics of the skin prevent infection

chemical and physical-dead epithelial cells, salt (sweat), amps

Why is the lymphatic system to important to immunity

What is an infection? (Think about it from the human point of view AND from the pathogen’s point of view)

pathogens in the body. the pathogens are trying to live and breed and infiltrate and the human cells are trying to kill them to prevent damage. 

the protein matrix on your cells that display either “self” proteins or “non-self” proteins; JUST the display

Major histocompatibility complex (MHC)

How does the MHC change between normal and infected cells

• normal cells display a small protein derived from normal cell processes (metabolism)

• infected cells display the same protein but have parts of the pathogen antigen attached

Which MHC class is located on body cells (anything other than WBCs)

MHC I

Which MHC class is located on immune cells

MHC II

Explain the difference between the MHC classes (1&2)

• MHC I is located on body cells and will display either self proteins for healthy cells or antigens for sick cells

• MHC II is located on immune cells and will display either self proteins for healthy cells or antigens to activate other immune cells

• summary: MHC I display antigens to identify an infected cell whereas MHC II displays antigens to activate other immune cells

T-lymphocyte that destroys infected body cells; also known as CD8

Cytotoxic “killer” cell

T-lymphocyte that coordinate the immune response; also known as CD4

helper cells

which t-lymphocyte would bind to an MHC I complex

Cytotoxic (CD8)

which t-lymphocyte would bind to an MHC II complex

Helper (CD4)

List the antigen-presenting cells (3)

dendritic cells, macrophages, and B-lymphocytes

what is the function of antigen-presenting cells

engulf pathogens and then present portions of their antigens to T-cells in the thymus or lymph nodes

explain how dendritic cells are the bridge between innate and adaptive immunity

they take the products of phagocytosis (innate) and show them to t-cells to stimulate the adaptive immunity response

briefly explain humoral (plasma-based) immune response

starts when a b-cell encounters a pathogen antigen (PAMP); antigen-receptor complex is brought into the cell which stimulates the cell to “clone” itself via mitosis, thus making more cells that are competent against the pathogen

explain b-cell proliferation

• variety of b-cells in lymph node, all with different antibodies

• antigen enters system, binds to the antibody that fits to it

• that b-cell will go through mitosis to “clone” itself

• clones (plasma cells) produce a bunch of antibodies and throw them into the plasma to stick to germs

what are plasma cells

• cloned b-lymphocytes that secrete antibodies to the antigen which will mark any cell with that antigen for destruction (opsonization)

• memory (B) cells are produce and exist for years to prime the immune system in case of reinfection

how long does b-cell proliferation take (production of antibodies)

3-6 days

what is the primary immune response

the 1st exposure to a pathogen; newly presented antigens cause B-lymphocyte clones to proliferate over 3-6 days

what is the secondary immune response

• anything beyond the first exposure to a particular pathogen

• the primed immune system can mount a much faster response when re-exposed to the same pathogen

• cloned cells left over from primary response bind better to antigens and live longer

what is active humoral immunity

• when YOU produce the antibodies in your body

• naturally acquired or through vaccination

why do you need to get booster shots

vaccines only expose the immune system to PAMPs, not the full pathogen, so the immune system can forget and needs to be reminded

what is passive humoral immunity

• immune response due to “artificial” antibodies from horses, rabbits, bacteria, etc.

• natural passive immunity includes breastfeeding

what are immunoglobulins

highly specific antibodies secreted by effector (turned-on) b-cells

list the five classes of immunoglobulins (Ig)

• IgM: large antibody (pentamer) released by plasma cells

• IgA: monomer and/or dimer released by mucus membranes

• IgD: acts as a B-cell receptor

• IgG: most abundant, small, can cross placental barrier

• IgE: involved in allergic reactions 

explain the basic antibody structure

• 2 heavy chains: identical structure, long

• 2 light chains: much shorter than H chains, loops around H chains

• variable (V) regions: changes depending on antibody; antigen binding site

• Constant (C) regions: very similar between antibodies in the same class

antigen-antibody pairings result in…

neutralization, agglutination, precipitation, complement fixation

this result of antigen-antibody pairings involves viral receptors or other virulence factors like toxins being bound and inactivated 

neutralization

this result of antigen-antibody pairings involves clumping of foreign cells when two or more pathogens bind to the same antibody

agglutination

this result of antigen-antibody pairings involves dissolved molecules (antigens) coming out of solution

precipitation

this result of antigen-antibody pairings involves bound antibodies attracting complement proteins that results in cell lysis 

complement fixation

explain antibody diversity

• antibodies are coded from hypervariable regions of DNA

• somatic recombination: few genes code the proteins that make up antigen receptors, but they are constantly shuffled, yielding millions of different combinations

what happens if a pathogen avoids the antibody response

the pathogen can hide in a cell, requiring a cell-mediate immune response via t-cell

what cells are we talking about when we say cell-mediate immune response

t-cells (CD4 and CD8)

T-lymphocytes are also known as…

immunocompetent cells

what does it mean to be an immunocompetent cell

• react to antigens present on body cells (MHC I)

  • bind to foreign antigens but don’t react strongly to self antigens

how does the body make sure only immunocompetent cells thrive

• positive selection: cells that don’t recognize, thus don’t bind to, MHC die via apoptosis

• negative selection: cells that bind too tightly to MHC die via apoptosis 

in order to activate t-cells against a particular pathogen, they must recognize…

BOTH self (MHC) and non-self (antigen)

explain CD4 t-cell activation

• antigen-presenting cell phagocytosed germ and presents antigen to t-cell

• both cells (antigen-presenting and t-cell) release cytokines (cell messengers that bind to and change other cells)

• in response to cytokines, t-cell clones itself

• clones produce different cytokines to activate b-cells and CD8 cells

explain how CD8 cells work

• once activated by cytokines released by CD4 clones, they will directly attack and kill pathogens or compromised body cells (virus-infected or cancerous)

  • they do this by recognizing foreign invaders by binding to antigens on MHC I and releasing perforins and granzymes

chemicals released by cytotoxic cells that punch holes in the foreign cell’s membrane

perforins

enzymes released by cytotoxic cells that degrade the interior of the foreign cell, resulting in cell lysis via apoptosis 

granzymes

explain CD8 t-cell activation

• cytotoxic cell binds to MHC I-epitope complex on an infected cell and produces granzymes and perforins

• perforins form pores in the plasma membrane as granzymes enter the cell and break down proteins, lysing the cell

what is the function of the immune system

to protect the body from infection and disease

the immune system’s ability to protect the body is based on…

the body’s ability to distinguish SELF from NON-SELF

the body determines something as “non-self” by the presence of…

antigens

what are the two immune branches

innate and acquired

the immune function present at birth

innate immunity

the immune function that develops over time from exposure to pathogens in the environment

acquired (adaptive) immunity

barriers to pathogens that are inherent at birth and do not require exposure to pathogens

innate immunity

what are two parts to innate immunity

integument and white blood cells

establishes a physical barrier between vulnerable cells and infectious agents 

integument

what are the two main barriers to pathogens involved in innate immunity

physical and chemical barriers

what are the physical barriers involved in innate immunity

dead dry skin cells and dendritic cells

modified monocytes that phagocytose invading microorganisms

dendritic cells

what are the chemical barriers involved in innate immunity (secreted by the skin)

high salt concentration, antimicrobial peptides (AMPs), lysozymes

chemical barrier that lyses bacterial cell membranes (bursts them)

lysozyme 

line all openings of the body and consist of epithelial cells with a basement layer of connective tissue (collagen)

mucous membranes

what are two ways that skin (epithelia) protects the body

• sheds skin cells carrying away pathogens

• chemical agents such as mucus that contains lysozymes and AMPs

what is the primary line of defense 

skin (integument)

leukocyte that produce histamines leading to inflammatory responses

basophils 

leukocyte that phagocytoses bacteria and viruses

neutrophils 

leukocyte that leads attacks against parasitic worms

eosinophils

what is the difference between granulocytes and agranulocytes

granulocytes have many organelles (lysosomes) that give them a grainy appearance, whereas agranulocytes have few or no organelles

leukocytes that live in the lymphatic system and either produce antibodies against specific invaders or destroy the invaders or cells infected by them 

lymphocytes

lymphocytes that produce antibodies specific to antibodies that leave the cell and stick to specific PAMPs to neutralize an infectious agent

B lymphocytes

lymphocytes that either produce cytokines that direct immune responses (CD4), or destroy infected cells (CD8)

T lymphocytes

why are lymphocytes the heart of adaptive immunity

they will remember the antibodies they produce (B cells) and be able to make them again quickly upon re-exposure to a pathogen (memory cells)

leukocytes that function to phagocytose bacteria and other invading pathogens and mature into macrophages which can perform diapedesis

monocytes

explain phagocytosis 

• WBCs surround and engulf pathogens

• then adhere to the pathogen via binding of cell membrane components (this process can be facilitated by opsonization)

• once adherence is complete, pathogens are engulfed via endocytosis, which forms a phagosome

• the contents of the phagosome are then digested by merging with a lysosome (phagosome + lysosome = phagolysosome)

what is it called when a pathogen is too big to be phagocytized so cells such as eosinophils and lymphocytes kill them by secreting toxic compounds directly onto them 

degranulation/toxin secretion

protein molecules released by host cells (infected cells) to inhibit virus spread by causing neighboring cells to produce antiviral proteins

interferons

proteins in the blood plasma that bind to pathogens and mark them for destruction (opsonization)

complement

other than opsonization, complement proteins can…

facilitate chemotaxis and produce membrane attack complexes (MACs)

when complement recruit WBCs to a pathogen

chemotaxis

complement can produce this which bores a hole in a pathogen’s membrane, effectively killing the cell

membrane attack complex (MAC)

quick, short-lived response to infection, usually beneficial

acute inflammation

long lasting response to infection, generally damaging and can cause disease

chronic inflammation

signs of inflammation

reddened skin, localized heat, edema, and pain

dilates blood vessels and makes them more permeable resulting in rapid healing and deliverance of more blood and resources to the site of infection, including phagocytes

(acute) inflammation

occurs when the presence of certain PAMPs (pyrogens) results in another chemical cascade that triggers the hypothalamus to increase the normal temperature of the body

fever

how does fever result in faster recovery from infection

increases the efficiency of complement and decreases pathogen replication rates

substances on cell surfaces or produced by cells that can provoke an immune response e.g. PAMPs (non-self!!)

antigens

complete antigens can…

• stimulate the proliferation of lymphocytes and antibodies (immunogenicity)

• react to activated lymphocytes and antibodies produced by the immune response (reactivity)

the immunogenic part of an antigen that antibodies or leukocyte receptors bind to to attack

antigenic determinants (epitopes)

very small molecules that are foreign to the body but NOT immunogenic

haptens