Some Immunological Test
Presented by
Alaa Faeiz
Ashwaaq Dyaa
Aseel Abd AL-Razaq
Supervised by D.Feras
Alaa Faeiz
Antigen -Antibody Reactions .
• Antigen – antibody reactions are performed to
determine the presence of either the antigen or
antibody. ( serological tests ).
• One of the two components has to be known.
• e.g. with a known antigen, such as influenza virus , a
test can determine whether antibody to the virus is
present or not .
There are different types of antigen antibody
ractions.
Include:
- Precipitation reactions(single and double)
- Agglutination reactions(latex,
haemagglutination and bacterial Ags )
-Labeled Antibody serology include:
-ELISA
-Immuno-fluorescence assay
- Radio Immuno Assay (RIA)
Precipitation test :
• In this test antigen is in soluble form (solution).
• Antibody cross -links antigen molecules to form
aggregates (precipitates) in the zone of
equivalence:at optimal proportion of antigen and
antibody.
• Precipitation test can be performed in solution or in
semi- solid medium (agar).
Precipitation in Agar.
• Single radial immunodiffusion:(MANCINI TEST)
• Antibody is incorporated into agar and antigen
introduced into the well.
• As antigen diffuses into agar precipitation rings form
depending on the concentration of the antigen.
• This technique is commonly used for determining the
concentrations of various plasma proteins such as IgG,
and IgM in patients suspected to be suffering from
agamma-globulinaemia and multiple myeloma,
respectively and others.
Single Radial Immunodiffusion.
Double immunodiffusion.(Ouchterlony analysis)
• Antigen and antibody are placed in different wells
in agar and allowed to diffuse and form
precipitation lines at the points of optimal
concentrations.
• This method is used to determine whether
antigens are related, identical or non –
identical.
Double immunodiffusion
Ashwaaq Dyaa
Agglutination
• In this test the antigen is particulate (e.g. bacteria and red
blood cells) or an inert particle (latex beads) coated
with antigen.
• Antibody is divalent and cross links the multivalent antigen
to form a lattice network or clumps
(agglutination).
• This reaction can be performed in a tube or on a glass
slide e.g. ABO blood grouping.
Latex agglutination
• This test is a laboratory method to check for
certain antibodies or antigens in a variety of
bodily fluids including saliva, urine,
cerebrospinal fluid, or blood. Examples of
tests based on latex agglutination reaction
include pregnancy test, C-reactive protein,,
and IgM rheumatoid factors and others.
• the sample is mixed
with latex beads
coated with a
specific antibody or
antigen. If the
suspected substance
is present, the latex
beads will clump
together
(agglutinate)
Antigen Antibody Reactions
• Haemaggultination
Tests:
The clumping or clustering
of red blood cells caused by
certain viruses, antibodies, or
other substances.
A.Simple haemagglutination
: when the red blood cells
agglutinated by anti sera
directed to them.
• B.passive
haemagglutination
Red cells can also
absorb many
antigens and when
mixed with specific
antibodies will form
clumps i.e. red cells
are passive carriers .
Agglutination test of suspensions
The most common example of this category
is “WIDAL TEST”
Widal test is a tube agglutination test
employed in the serological diagnosis of
enteric fever . Patients' suffering from
enteric fever would posses antibodies in
their sera which can react and agglutinate
serial doubling dilutions of killed , coloured
salmonella antigens in a tube agglutination
test .
A. Rapid screening test
1)Place 2 drops of patient's serum .
2)Add 1 drop of the suspension (S.typhi and
S.paratyphi ,A and B for H and O antigen ) .
3)Mix and read within 1 minute .
• B. tube test, also known as a culture tube or sample
tube, is a common piece of laboratory glassware
consisting of a finger-like length of glass or clear plastic
tubing, open at the top, usually with a rounded U-shaped
bottom. Tube agglutination test fordetermining antibody
titer
The procedure is done as follows :
1)Dilute patient serum in normal saline
(1\20 ,1\40 ,1\80 1\160 ,1\320 ,1\640
,1\1280).
2)Add 1 drop of the suspension.
3)Mix and incubate (O antigen at 50 °C
for 4hrs ,while H antigen at 50 °C for
2hrs) .
4)Examine for agglutination at the bottom
of the tube.
c.Rapid slide titration
Similar to rapid screening test ,but known
quantities of serum are added (e.g. 80 ul, 40
ul, 20 ul, 10 ul, 5 ul, 1.0 give dilution of 1\20 ,
1\40 , 1\80 , 1\160 , 1\320 respectively) .
Aseel Abd AL-Razaq
Enzyme Linked Immunosorbent Assay (ELISA)
• has become one of the most widely used serological tests for
antibody or antigen detection.
• ELISA include:
• Direct and Indirect immunosorbent assay .
• The direct ELISA is used to detect antigens against a specific
antibody bound in a test well.
• The indirect ELISA is used to detect antibodies against an antigen
bound in a test well.
• ELISA techniques use antibodies linked to an enzyme and
Antigen- antibody reactions are detected by enzyme activity.
Direct ELISA
• Direct ELISA for antigen detection.
• A common use of the direct ELISA test is to detect the
presence of drugs in urine. For this test,antibodies specific
for the drug are adsorbed to the well on the microtiter
plate. When the patient's urine sample is added
to the well, any of the drug that it contained would bind to
the antibody and is captured . The well is rinsed to remove
any unbound drug.
• To make a visible test, more antibodies specific to the drug
are now added (these antibodies have an enzyme attached
to them- therefore, the term enzyme-linked ) and will react
with the already-captured drug, forming a "sandwich" of
antibody/drug/enzyme-linked antibody This positive test
can be detected by adding a substrate for the linked
enzyme; a visible color is produced by the enzyme reacting
with its substrate and then we measure by
spectrophotometry.
Direct ELISA
ELISA
Intensity of color correspond to
concentration of antibody.
Indirect ELISA
• The indirect ELISA test, detects antibodies
in a patient's sample rather than an antigen
• Indirect ELI SA tests are used, for example,
to screen blood for antibodies to HIV .For
such a purpose, the microtiter well contains
an antigen, such as the inactivated virus that
causes the disease the test is designed to
diagnose,
• A sample of the patient's blood is added to
the well; if it contains antibodies against the
virus, they will react with the it. The well is
rinsed to remove unbound antibodies, If
antibodies in the blood and the virus in the
well have attached to each other, they will
remain in the well-a positive test,
• To make a positive test visible, some anti-H ISG (an
immunoglobulin that will attach to any antibody, including
the one in the patient's serum that has attached to the virus
in the well)is added, The anti-HISG is linked to an
enzyme, A positive test consists of a "sandwich" or a
virus/antibody/enzyme-linked-anti-HISG, At this point, the
substrate for the enzyme is added, and a positive test is
detected by the color change caused by the enzyme linked
to the anti-HISG.
Indirect ELISA
Thank You
