ENHANCEMENT CLASS: ANTIGENS AND ANTIBODIES INTERACTIONS Flashcards
Study of fluid component of blood
SEROLOGY
What body fluid usually used in Serology?
SERUM
Can other body fluids can be tested? Yes or No
Yes
What tube usually used in Serology?
Red Top/Gold Top Sterile Tube
What tube usually used in Serology?
Red Top/Gold Top Sterile Tube
Spin to separate serum from cellular components
SEROLOGY
In practice, the term _____ usually refers to the diagnostic identification of antibodies in the serum
SEROLOGY
Substances that have the ability to bind with an antibody, but may or may not evoke an immune response
ANTIGEN
antigens capable of inducing an immune response, such as formation of antibody or sensitized T-cells.
Contain structure recognized as foreign by the immune system
IMMUNOGENS
All immunogens are antigens. But, not all antigens are immunogens. T OR F?
TRUE
Specific portion of macromolecular antigen to which an antibody bind
EPITOPE (Antigenic determinant)
- Part of an antibody which recognizes and binds to an antigen
- The uniqueness of a paratope allows it to bind to only one epitope
PARATOPE (Antigen-binding site)
Not all surfaces act as antigenic determinants. T OR F?
TRUE
antigEn-Epitope (EE)
antibOdy-Paratope (OP)
GETS?????
- Formerly known as “gamma globulins”
- Located w/in gamma through beta region of serum electrophoresis
ANTIBODY
Specific glycoproteins referred to as ____
immunoglobulins
Specific glycoproteins referred to as ____
immunoglobulins
Two forms of antibody:
Cell surface (membrane-bound) Secreted Ig’s (antibodies)
Can be found in blood plasma and in many body fluids (tears, saliva, colostrum)
Antiserum (antibody-containing serum)
ANTIBODY
Basic structural unit of antibody
MONOMER
Basic structural unit of antibody
MONOMER
Consist of ___ polypeptide chains (tetrapeptide)
4
Consist of four (4) polypeptide chains (tetrapeptide)??
1 pair of Heavy chain
1 pair of Light chain
Polypeptude chains are linked together by ____
disulfide bonds
Is each pair of polypeptide chains are identical?
Yes
what is the Three Globular structure
- 2 Fab (Fragment antigen binding) region
- 1 Fc (Fragment crystallizable) region (crystallizes at 4 deg C)
is the study of IN-VITRO antigen-antibody
reactions
Serology
– is a substance (self/non-self) which elicits
an immune response
Antigen
a specific protein which is produced in response to an immunogen
Antibody
Antibody molecules combine _______with antigens to form immune complexes
REVERSIBLY
Antigen + Antibody =???
AgAb complex
The detection and measurement of these reactions form the basis of immunology and serology
AgAb complex
The binding of antigen and antibody depends on:
Affinity
Avidity
Relative proportions of antigen and antibody present
Initial force of attraction that exists between a single Fab site on an antibody molecule and a single epitope on the corresponding antigen - Weak binding
AFFINITY
If antibody is specific to antigen
Stable binding (Lock-and-key model)
other antigen resembles original
antigen
Cross-reactivity
Assay is more sensitive (Reactions are visualized easily
High affinity
Force that keeps the molecule together
AVIDITY
Represents the overall strength of antigen-antibody binding and is the sum of the affinities of all the individual antibody-antigen combining sites
AVIDITY
Measure of overall stability of ag-ab complex
AVIDITY
The more bonds are form = ???
the higher the avidity
What antibody has has highest avidity??
IgM
The higher the affinity and avidity, ________
the lesser the tendency of ag-ab complex dissociation
- Increased amount of ag-ab complexes
- Reactions are visualized more easily
AFFINITY AND AVIDITY
RELATIVE PROPORTIONS OF ANTIGEN AND ANTIBODY PRESENT (PRECIPITATION CURVE)
Lattice formation
Lattice formation:
Zone of Equivalence
Zone of Equivalence was formulated by??
Dr. Philippa Marrack
False Negative in Zone of Equivalence:
Excess Antibody
Excess Antigen
Excess Antibody:
Prozone
Excess Antigen:
Post zone
One of the simplest methods of detecting antigen antibody reactions
PRECIPITATION
Most antigens are multivalent???
YES
capable of forming aggregates in the presence of the corresponding
antibody
multivalent
visible insoluble complexes (precipitate out of the solution)
Soluble antigen + soluble antibody =
________is better at precipitation than IgM
IgG
In today’s clinical laboratory, precipitation reactions are
most commonly measured by ___
automated methods
Example of automated methods
Immunoturbidimetry (light blocked)
Nephelometry (light scattered)
Insoluble antigen (agglutinogen) + soluble antibody (agglutinin) = visible aggregates (clumping)
GETS?
2 PHASES OF AGGLUTINATION
Sensitization
Lattice Formation
antigen-antibody binding through single epitopes on particle; rapid and reversible
Sensitization
stabilization of complexes with the
binding together of multiple epitopes (formation of cross-links)
Lattice Formation
FACTORS INFLUENCING AGGLUTINATION
Nature of antigen
Zeta potential
enough epitopes should be
present, they should not be obscured
Nature of antigen
negative charge around cells like
RBCs, causing them to repel each other at a distance of 25 nm; due to sialic acid found on surface of RBC
Zeta potential
Remedy for factors affecting agglutination:
- Proteolytic enzymes to cleave sialic acid
- Potentiators like albumin and polyethylene glycol (PEG) to remove water – decreased ZP
- Low ionic strength saline (LISS)
IgM > IgG
GETS?
IgM size:
35 nm
IgG size:
14 nm
If antibody is IgG, _____________ can be used
anti-human globulin (AHG) or Coombs reagent
IgM temperature:
4 to 27 degrees Celsius
IgG temperature:
30 to 37 degrees Celsius
Shaking (used for cards or slides), centrifugation (used for tubes)
hastens reaction