Immunology Lab 2

Question 1

precipitation

Answer 1

the reaction of a specific antibody with a SOLUBLE antigen to form an insoluble lattice Ag-Ab complex

Question 2

agglutination

Answer 2

the reaction of a specific antibody with a PARTICULATE antigen to form a visible clump

Question 3

particulate antigen

Answer 3

antigens that will not mix into solution; attached to beads

Question 4

3 Requirements for Optimal Ag-Ab Reaction

Answer 4

1. Ab should be at least bivalent (have two or more binding sites)
2. Ag should be multivalent (have multiple epitopes)
3. Ratio of Ag-Ab should be in the equivalence zone

Question 5

equivalence zone

Answer 5

the region where the maximum amount of precipitation occurs

Question 6

IgG is ___valent

Answer 6

bivalent (2)

Question 7

IgM is ___valent

Answer 7

multi (10)

Question 8

What are the three zones?

Answer 8

1. Antibody excess (this is what’s bound to the bottom in vitro)
2. Equivalence
3. Antigen excess

Question 9

For in vivo reactions, what zone will result in disease?

Answer 9

antigen excess - overwhelms the #/ability of Ab to bind so the macrophages in the body cannot fight it off

Question 10

Agar Double Diffusion

Answer 10

place dilutions of serum (Ab) in wells surrounding a center well of Ag; 24-48 hours look for a precipitin line where the two meet to determine titer

Question 11

What two factors can affect location and shape of the precipitin line?

Answer 11

1. Molecular Weight (line closer/curved to that of higher MW)
2. Concentration of the Ab (larger dilutions pull the line closer/curved towards the Ab/outer well; doesn’t travel as far because there isn’t as much of it)

Question 12

What can you use agar double diffusion for clinically?

Answer 12

titers of bacterial, viral, and fungal infections (including Blastomyces and Histoplasma)

Question 13

How are titers reported?

Answer 13

as the inverse of the dilution (1:4 –> titer = 4)

Question 14

Hemoagglutination

Answer 14

agglutination of RBCs

Question 15

Clinical Application of Hemoagglutination?

Answer 15

blood typing

Question 16

Why can an antibody not be univalent (rare anyway) in an agglutination reaction?

Answer 16

no clumping could occur! A singular Ab would not be able to bind multiple antigens on cells together

Question 17

Rheumatoid Factor

Answer 17

IgM anti-IgG autoantibodies (meaning an IgM that contains Fc regions specific for canine IgG)

Question 18

Rheumatoid Arthritis

Answer 18

chronic crippling disease [in dogs] involving inflammatory infiltrate in the joint(s) that can eventually lead to its destruction

Question 19

How accurate is diagnosing rheumatoid arthritis (RA) in dogs with a latex agglutination reaction?

Answer 19

~70% of dogs that have RA will be positive with this test (the rest of the diagnosis comes from clinical symptoms)

Question 20

Is rheumatoid factor found in diseases besides RA?

Answer 20

yes - lupus erythematosus

Question 21

Rheumatoid Arthritis Agglutination Test

Answer 21

serum put in well (the flat black plate) and mixed with a suspension of latex beads coated in IgG; clumps will form in positive patients

Question 22

Is an Ag-Ab reaction permanent?

Answer 22

no - it is reversible (noncovalent) binding and the reactants are not chemically altered

Question 23

affinity

Answer 23

combined strength of bonding between a single Ag binding site (Fab) on the Ab and a single epitope on the Ag

most bonds over the shortest distance

Question 24

Do we want low or high affinity Abs?

Answer 24

High!

Question 25

noncovalent bond types associated with Ab affinity (4)

Answer 25

1. Hydrogen bonds
2. Electrostatic bonds
3. Hydrophobic bonds
4. Van der Waals forces

Question 26

avidity

Answer 26

measure of the overall strength of multivalent binding (ex: IgM has higher avidity than IgG)

Question 27

specificity

Answer 27

ability of an Ab to distinguish b/n the immunogen that elicited it and other related Abs

Question 28

cross reactivity

Answer 28

ability of an Ab elicited by an Ag to bind to an unrelated Ag that just happens to be around and fits the script