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Interpretation of Serologic Tests

I. IntroductionA. Serology

B. Antiserum commercially prepared solutions of antibodies (Ab)

II. Types of Serological Tests

A. Precipitation Reactions occurs when theres formation of lattices (formed when

antigenbinds with Ab), which occurs in the zone of equivalence (equal proportion of antigen

and Ab)

1. Precipitin Ring Tests --- antigens and Ab diffuse towards each other at the

zone ofequivalence (precipitin ring); antigens must be soluble.

2. Immunoelectrophoresis --- in the patients serum, if a patient has a

disease(HIV) there

are antigens of bacteria, these antigens are separated by electrophoresis and areseparated by a filter (nitro-cellulose filter), a dye-labeled enzyme is washed over

the filter, if antigens are present it will produce a visible color change (antibodybound to antigen).

B. Agglutination Reaction (clumping) utilize antibody and particulate antigens.

1. Direct Agglutination Tests --- think of contact lens cases having severalwells

containing antigens and antibodies; each well contains half the antiserum of the

previous well but the particulate antigen is the same for each well; darker areameans there is agglutination, antibody-antigen complexes settle at the bottom;

when there are not enough Ab to bind with antigen the Ab will go to the bottomof the well; take note of the most dilute concentration where there isagglutination.

2. Indirect (Passive) Agglutination Tests --- use latex beads or minute latex

spherescoated with antigen or antibody. It is a positive direct test for antibodies if latex

beads are coated with antigen and positive for antigens if the latex beads are

coated with antibodies.

3. Hemagglutination (viral) --- in the presence of viruses there ishemagglutination of

RBCs; clumping of the RBCs.

C. Neutralization Reactions harmful effects of antigens are neutralized/blocked by

the

antibodies.1. Viral Hemmaglutination Inhibition Test --- if there are antibodies to the

virus,

hemagglutination does not occur; without antibodies there will be agglutination of

the RBCs caused by the antigens.

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D. Complement-Fixation reactions 2 stages: (1) Complement-fixation stage

(2) Indirect stage

E. Enzyme-Linked Immunosorbent Assay (ELISA) make use

of micro-titer plate (depressions/wells)1. Direct ELISA --- sandwich(antibody, antigen, enzyme-lined Ab specific

for antigen);

if antigen is present there is visible color change, detects presence of antigen.Example: Pregnancy Test Kit

put drops of urine on drop window

2. Indirect ELISA --- attached to well is antigen, add antiserum with Abs

from patient, there is binding of antigen and Ab, then enzyme-linked antihuman

immune serum globulin; these form a sandwich, add enzyme substrate, color change

indicate presence of antibodies.

F. Fluorescent-Antibody Techniques

1. Direct Fluorescent-Antibody --- test for antigens2. Indirect Fluorescent-Antibody --- test for antibodies

G. Radioimmunoassay