Module 3: Antigen-Antibody reactions Flashcards Preview

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Flashcards in Module 3: Antigen-Antibody reactions Deck (17)
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1

5 antigen-antibody reactions

neutralization
agglutination
precipitation
complement fixation
Sensitization (opsonization)

2

Neutralization

when antigen is bound to an antibody the activity of antigen may be neutralized or inhibited

3

Agglutination

Used in TM lab
If RBC has the A antigen, the cell will react with anti A antisera to form agglutinates

4

Precipitation

soluble antigen when combined with an antibody may precipitate out
Can be seen and measured to quantitate the amount of antigen present

5

Complement fixation

in lab, if complement fixation proceeds to completion, the end result is hemolysis (visible)

in pt, antibody binds to antigen on a cell surface and can activate complement

6

Sensitization (opsonization)

In vivo- antigen/antibody binding promotes phagocytosis

in vitro- sensitization not visible; use an additional antibody (antihuman globulin) to bridge the gap between antibodies coating the antigen, producing visible agglutination

7

Antigen and antibody are held together by

forces acting together to keep the complex stable

Ionic bonding (oppositely charged groups)
Hydrogen bonding (electronegative atoms for hydrogen)
Van der Waals forces (weak attraction between electron cloud of an atom and the protons of the nucleus of other atom)
Hydrophobic forces (attraction of non-polar groups to one another)

8

Affinity

the strength with which the idiotype grabs onto the epitope

9

factors affecting the affinity constant

pH (optimum 6.5-7.5)
Ionic strength of reaction solution (Lower ionic strength = increased rate of association between Ab and Ag)
Concentration of reactants
Temp
Incubation time

10

Avidity

the overall binding energy between multivalent antibodies and multivalent antigens

11

Prozone

concentration of antibody exceeds that of antigen and lattice formation does not occur

12

postzone

the concentration of antigen exceeds that of antibody and lattice formation is impossible

13

zone of equivalence

in between prozone and postzone layer where antibody and antigen concentration are proportionate and a lattice is formed
Maximum precipitation occurs in this zone

14

heterophile antibodies

a group of cross-reacting antibodies. These antibodies are produced in response to one antigen, but also react with an unrelated but structurally similar antigen

15

Elution

the process of removing and antibody from and antigen in vitro

16

4 different processes of elution

changing pH
increasing ionic strength of the solution
heat
organic solvents

17

Antibody titre

determines relative concentration of an antibody in a serum sample
The reciprocal of the last dilution to visibly demonstrate the antibody