L11 Antigens And Antibodies

Question 1

What are antigens

Answer 1

Immunogens that react with specific receptors on b cells or t cells and stimulates a specific immune response

Question 2

What must the substance be in order to be classified as immunogenic

Answer 2

Foreign to body

Question 3

What are the most potent immunogens

Answer 3

Proteins with high molecular weight

Question 4

What are some examples of antigens

Answer 4

Polysaccharides,lipopolysaccharide, lipoproteins and nucleoproteins

Question 5

What are haptens

Answer 5

Molecule that is not immunogenic by itself
They can be small molecules, nucleic acids lipids or drugs ex penicillin
Cannot stimulate a primary adaptive response except when bound to a carrier protein

Question 6

How is the hapten strategy used

Answer 6

In conjugate vaccines

Weak immunogen is conjugated to a small strong peptide antigen

Question 7

What are super antigens

Answer 7

Viral and bacterial proteins that cross link the variable b domain of a t cell receptor to the (MHC) class 2 of antigen presenting cells outside normal peptide binding groove

Question 8

What does the cross linkage of MHC with variable b domain of t cell do

Answer 8

Activation of signal that induces t cell activation and proliferation in absence of antigen specific recognition of peptides

Question 9

What is the consequence of super antigens binding to outside of antigen binding cleft

Answer 9

Activate any clones of t cells expressing a particular variable b sequence and thus cause polyclonal activation of t cells resulting in over production of pro inflammatory cytokines which can lead to systemic toxicity

Question 10

What are the molecules produced during infectious process that act as super antigens

Answer 10

Staphylococcal enterotoxins
Toxic shock syndrome toxin
Exfoliative dermatitis toxin
Streptococcal pyrogenic exotoxins

Question 11

How are antibodies expressed

Answer 11

Soluble molecules present in serum and tissue fluids and function to protect against microbes extracellular pathogens in blood mucosal surfaces and tissues
Membrane bound antibodies on the surface of b cells function as antigen receptor

Question 12

What is the major immunoglobulin present in serum

Answer 12

igG

Representing appox 75% of serum antibodies in humans

Question 13

What does IgG consist of

Answer 13

Two L chains and two H chains held by disulphide bridges

Divided in to variable and constant regions

Question 14

How many variable and constant domains does L chain and H chain have

Answer 14

L chain: one and one

H chain: one variable and three or more constant

Question 15

What is the function of variable and constant domain in igG

Answer 15

Variable: involved in antigen binding
Constant: responsible for biologic functions

Question 16

How many subclasses are there for igG

Answer 16

4

Question 17

What are protective functions of IgG

Answer 17

Activates complement leading to cell lysis
Acts as an opsonin enchancing phagocytosis
Neutralizes pathogens and toxins
Mediates antibody dependent cell mediated cytotoxicity:lytic destruction of tumor or infected cells mediated by killer cell and binds to Fc portion of bound antibody

Question 18

Only antibody that crosses placenta

Answer 18

IgG

Question 19

% of igM in serum and how many units does it consist of and how are they joined together

Answer 19

7%

5 units by j chain

Question 20

Highest mol weight of Ig

Answer 20

IgM

Formed of 10 L and 10 H

Question 21

Ig that appears early during specific immune response

Answer 21

IgM

Most effective at activating complement

Question 22

Major immunoglobulin responsible for mucosal immunity

Answer 22

IgA

Question 23

Level of igA in serum

Answer 23

10-15%

Question 24

Predominant class of ig found in extravascular secretions such as milk saliva and tears, respiratory intestinal and genital tracts?

Answer 24

IgA

Question 25

When is igA a monomer and when is it a dimer

Answer 25

Monomer in serum

Dimer when secreted (2 monomers that contain additional polypeptides)

Question 26

What stabilizes secretory igA

Answer 26

J chain and a secretory component that is incorporated in to igA when its being transported through an epithelial cell

Question 27

How many subclasses of igA are there

Answer 27

2

Question 28

Ig mainly on surface of b lymphocytes

Answer 28

IgD

Question 29

Ratio of igD and igM in b cells

Answer 29

3 to 1

Question 30

Also called cytotropic Ab

Answer 30

IgE

Question 31

What does igE do

Answer 31

Binds directly to Fc receptors present on mast cells,eosinophils and basophils
Involved in elicitation of protective immune responses against parasites and allergens

Question 32

How does ig class switching occur

Answer 32

Initially all b cells bound to an antigen carry igM specific antigen and produce igM in response to this antigen.
Later,gene rearrangements generate antibodies of same antigen specificity but of diff ig classes so that the ig produced later has the same specificity as original igM but with diff biologic characteristics
Dependent on cytokines released from T cells

Question 33

What are MABS

Answer 33

Highly specific antibodies produced against a single epitope

Question 34

How are mabs obtained

Answer 34

By fusion of a myeloma cell with a b cell producing antibodies against a single epitope(derived from spleen of mice)
Hybridoma cell is result

Question 35

What is the ability of a hybridoma cell

Answer 35

Has ability to produce unlimited quantities of a highly specific monoclonal antibody (murine type)
Humanized one produced by genetic eng

Question 36

Diagnostic uses of MABS?

Answer 36

As in lymphocyte subsets determination

HLA typing and serological tests as ELISA,chemiluminescence and immunofluorescence

Question 37

Therapeutic uses of MABS?

Answer 37

Anti tumor therapy,antiallergic, and immunosuppressive therapy to prevent graft rejection

Question 38

Monomers
Dimers
Pentamer
In igs

Answer 38

Monomers
IgD,igE,igG
Dimer
igA
Pentamer
IgM