immunology set 3

adaptive defenses (2)

• humoral immunity (B cells)

• cellular immunity (T cells)

both the T and B cells are..

lymphocytes

the key difference between the innate and adaptive immune responses is the way they...

recognize pathogens; different types of receptors

specific acquired immunity (4)

the ability to recognize and defend against pathogens, pathogen products, and abnormal body cells

-systemic
-specificity
-memory

antigens

substances recognized as foreign by the immune responses, which reacts with antibody

immunogens

agents capable of inducing an immune response

examples of immunogens

vaccines, macromolecules, microbes...

the specific immune response has 2 components:

primary and secondary immune response

CD of B cells

CD19, CD20, 40

why can B cells bind free antigens?

because they can process them by itself; it is apart of the APC's..

what are B cells identified by?

cell-surface glycoproteins specific for both cell type and stage of differentiation: CD 19,20,40

B cells originate from...

stem cells in the bone marrow, B-lymphocytes, or B cells (from avian bursa of Fabricius)

where do B cells cluster after differentiating within the bone marrow?

in the germinal centers of lymph nodes and in the lymphoid follicles of the spleen

the B cells account for \___% of circulating peripheral blood lymphocytes

15

characteristics of antigens (5)

immunogenicity, specific reactivity, foreigners, size and shape

characteristics of antigens: immunogenicity

the capacity to stimulate production of specific, protective humoral or cellular immunity

characteristics of antigens: specific reactivity

the capacity to be recognized by the produced antibodies and T cells

characteristics of antigens: foreignness

must be recognized as non self; foreign proteins are excellent antigens

characteristics of antigens: size

must have molecular weight of at least 10kd to be recognized

characteristics of antigens: shape

tertiary and quaternary structures define extent of antigenicity

epitopes

antibody-binding site on an antigen for a specific antibody

epitopes are also known as

antigenic determinants

small part of antigen that determines the specificity of the reaction with an antibody and triggers the immune response is \___

epitope

haptens

smaller substance that can not trigger an immune response unless attached to body protein or to an antibody molecule already formed

examples of haptens

poison ivy, animal dander, detergents, and cosmetics

diversity of antigen receptors

• human immune system able to recognize and bind to at least a billion different epitopes

• result of genetic recombination- shuffling and rearranging of a few hundred versions of several small gene segments

each B or T cell has its own unique set of gene segments that code ????

its unique antigen receptor in the cell membrane

cell surface receptors: innate

PRR's

cell surface receptors: acquired

somatically generated receptors:
BCR and TCR

B-cell receptors

surface plasma membrane receptor that binds to a specific antigen

B cells bind \___ antigens

FREE

T cells bind \____ antigens

PROCESSED

what do T cells populate? (2)

1: paracortical and deep medullary areas of lymph nodes

2: periarteriolar sheaths of the spleen

T cells account for approximately __% of circulating peripheral blood lymphocytes

70%

T cells are sub-classifed by surface markers into:

CD4+ (Th) -\> helper
CD8+ (Tc) -\> cytotoxic

CD4+ account for approximately __% of circulating T cells

60

CD8+ account for approximately __% of circulating T cells

30

normal ration of CD4+ and CD8+

2:1

cell-mediated immunity (CMI) refers to destruction of antigens by?

T cells

CMI is particularly effective against \_______

intracellular pathogens

CMI always involves cells attacking cells, releasing

cytokines

examples of intracellular pathogens

viruses, fungi, parasites

antibody-mediated (humoral) immunity (AMI) refers to destruction of antigens by ???

antibodies (Ig)

mature T cells (4)

Helper T cells and Cytotoxic T cells
Memory T cells
Regulatory T cells (Tregs)

memory T cells

remember antigen and quickly stimulate immune response on reexposure

regulatory T cells

control the T-cell response. suppress T and B cells function (immune privileged mediators)

helper T cells

activate macrophages, B cells and T cells

cytotoxic T cells or "killer T cells"

destroy pathogens and release chemicals called cytokines

associated with MHC-I

initial exposure to a particular infectious agent, or immunogenicity, is followed by an ??

induction phase

induction phase

precommihted lymphocytes that on subsequent contact with that agent, proliferate and mature into B or T cells

B cells: primary immune response

antibody (Ig)-secreting plasma cells (humor response), secrete IgM

specifically reactive T cells: primary immune response

secretes various mediators (lymphokines)

does a pathogen provoke either B, T or both cell types of induction pahse?

usually both

the first introduction of each type of antigen into the immune system selects a...

genetically distinct lymphocyte

lymphocyte specificity is \___, existing in the genetic makeup before an antigen has ever entered the system

preprogrammed

antigen stands for

antibody generator

antigens AKA

immunogens

antigens get past the body's \___ defenses

nonspecific

what are the 3 ways in which antigens get past the body's non-specific defenses

1. enter the bloodstream to be deposited in spleen

2. penetrate the skin and end up in lymph nodes

3. penetrate mucous membrane and lodge in lymphoid tissues

each B cell antigen receptor is a Y-shaped molecule with two \_____ and two \_____

identical heavy and light chains

the variable regions of the BCR provide

antigen specificity

T cells bind to

antigen fragments displayed or presented on a host cell

what interaction for the TCR is necessary for the T cell to participate in the adaptive immune response

• T cells bind to antigen fragments displayed or presented on a host cell

• these antigen fragments are bound to cell- surface proteins called MHC molecules.

• a T cell can then bind both the antigen fragment and the MHC molecule

B cells sit in..

lymph nodes, spleen or Peyer's patches and lets antigens be brought to them

once B cells are activated, they do what?

different tie not plasma cells that secrete antibodies

AMI works mainly against...

antigens dissolved in body fluids and extracellular pathogens (toxins and bacteria) that multiply in body fluids but rarely enter body cells

B cells express Ig on

its surface

once the Ig is expressed on the B cells surface, it interacts with its homologous antigen and...

is triggers to proliferate and differentiate into plasma cells

the plasma cells excrete vast quantities of \___ that is specific for the same antigen that originally triggered the B cell

Ig

antibodies (immunoglobulins)

heterogenous gorupof proteins (MW: 150,000-900,000kd) that contain carbohydrates. therefore glycoproteins

antibodies (immunoglobulins) are found predominately in

the gamma globulin fraction of serum

Ig constricts of...

polypeptide chains linked by disulfide bonds, such that each antibody contains a minimum of two identical heavy (H) chains and two identical light (L) chains

2 light chains exist...

kappa or lambda and each antibody has one or the other type

antibodies (Abs) have antigen-binding capacity defined by their

specific H and L chains

one end of the Ig binds to...

the Fab portion of antigens

Fab stands for

fragment (of the molecule which is) antigen binding

Fc stands for

and is responsible for

crystallizable

responsible for effector functions

the basic antibody structure consists of

four looping polypeptide chains linked together by disulfide bonds

variable regions of each arm of the antibody structure combine to form?

2 identical antigen-binding sites

the tips of the antibody are

variable regions (V) and form FAB

constant region of antibody

terminal that contains 2 heavy chains; remains same for certain class of antibodies; determines characteristics (class) of antibody; where complement binding takes place

antibody actions

1. neutralizing antigen

2. immobilizing bacteria

3. agglutinating and precipitating antigen via cross-linking

4. activating complement

5. enhancing phagocytosis

how do antibodies enhance phagocytosis?

through precipitation, complement activation or opsonization (coating with special substance)

how do antibodies neutralize antigens?

by blocking effects of toxins or preventing its attachment to body cells

which class of antibodies are the first to be produced?

IgM

"surface antibody" on surface membrane of B cells

IgM

most abundant class of antibodies

IgG

dimer antibody

IgA

surface IgM binds directly as

integral membrane protein

IgM shape

pentameric

are there 2 types of IgA

yes!

which class of antibody is themes common and most active at mucosal surfaces and other secretions

IgA

IgA molecules receive a \____ component from the epithelial cells into which they pass

secretory

IgA is abundant in

saliva, tears, and breast milk

IgA provides the primary defense at

mucosal surfaces. helps prevent entry of pathogen

IgG is the most abundant class of antibody in the \_____

blood

75-85% of antibodies in plasma

there are \___ subclasses of IgG which are all \_____ and they usually have high affinity for antigen

4

monomeric

unlike IgM, IgG is able to

leave the bloodstream and enter tissues

which class of antibody is the only one to pass the placental barrier

IgG

which class of antibody provides the only protection for newborns?

IgG