2. Time to recollect !!!
• Antigen?
• Antibody?
• Antigen antibody reactions?
3. Complement Fixation Test (CFT)
• What is a complement ?
• Antigen antibody complex – bound by
complement – mediates bacterial clearance,
viral neutralisation, lysis of RBC
5. Procedure
• Heat inactivation of the antiserum – to inactivate the
complementary activity of serum
• The source of the complement is guinea pig serum.
• Complement – heat labile
• Freshly draw the serum
6. Ingredients
• CFT has two steps and five reagents
• Antigen
• Antibody
• Complement
• Sheep erythrocytes
• Amboceptor ( Rabbit antibody to sheep red
cells)
9. Wassermann reaction
• Formerly used for the serodiagnosis of syphilis
• Procedure
1. Lysis of erythrocytes – Negative CFT
2. No lysis of erythrocytes – Positive CFT
• For every test, appropriate controls should be
added.
10. Other complement dependent tests:
• Immune adherence-T.pallidum, V.cholerae
• Immobilisation test – Treponema pallidum
• Cytolytic or cytocidal test- V.cholerae
11. Conglutination
• Some donot fix the guinea pig serum
complement
• Use indirect CFT or conglutination test
• Use sheep RBC with bovine serum
• Bovine serum – conglutinin – beta globulin –
antibody to complement
12. NEUTRALISATION TESTS
• Virus neutralisation tests:
1. Neutralisation of viruses by their antibodies
and are demonstrated in cell cultures, eggs
and animals
2. Neutralisation of bacteriophages by the
plaque inhibition test
13. Toxin neutralisation tests
• Bacterial exotoxins - induce neutralising
antibodies(antitoxins) protection against diseases
such as diphtheria and tetanus.
• In vivo tests:
1. Toxigenicity test-detection of toxin of C.diphtheriae
2. Schick test
• In vitro tests:
1. Anti streptolysin O (ASO) test
2. Virus neutralisation test
3. Nagler reaction-rapid detection of C.welchii
14. OPSONISATION TEST
• Opsonisation - process by which a particulate
antigen becomes more susceptible to
phagocytosis.
• Opsonin – is then identified as a complement.
• Bacteriotrophin – heat stable serum factor
with similar activity Specific antibody
15. • Opsonic index ratio of the phagocytic
activity of the patients blood for a given
bacterium, to the normal individual.
• Measured by incubating fresh citrated blood
with the bacterial suspension at 37deg C for
15 minutes
• Phagocytic Index: Estimating the average
number of phagocytosed bacteria per PMN
from stained blood films
16. Immunofluorescence
• Fluorescence ?
• Immuno fluorescence ?
• Types – Direct and indirect
• The commonly used fluorescent dyes are:
i) Fluorescin isothiocyanate (Blue green
fluorescence)
ii)Lissamine rhodamine (orange red fluorescence)
18. Uses
1. It is commonly employed for detection of bacteria,
viruses or other antigens in blood, CSF, urine,
faeces, tissues and other specimens
2. It is a sensitive method to diagnose rabies by
detection of the rabies virus antigens in brain smears
Disadvantage
• Separate specific fluorescent labelled antibody has to
prepared against each antigen to be tested
20. RADIOIMMUNOASSAY (RIA)
• Berson and Yallow (1959) first described RIA
• Radioimmunoassay is widely-used because of
its great sensitivity
• RIA detect antigens upto picogram (10−12 g)
quantities
29. Chemiluminescence immunoassay
(CLIA)
• Chemiluminescence - Chemical reaction emitting
energy in the form of light
• Chemilumiscence compounds - Luminol or
acridinium esters .
• Signal can be amplified, measured, and the
concentration of the analyte calculated
• The method is fully automated
• Uses - where the volume of work is large
- drug sensitivity testing of M.tuberculosis
31. Immunoelectroblot/Westernblot
• Immunoblot or westernblot techniques
combine the sensitivity of enzyme
immunoassay with much greater specificity.
• Western blotting – Proteins
• Northern blotting – RNA
• Southern blotting - DNA
33. Western Blot for detection of HIV antibody
HIV-1 Western Blot
• Lane1: Positive Control
• Lane 2: Negative Control
• Sample A: Negative
• Sample B: Indeterminate
• Sample C: Positive
35. Flow cytometry
• An instrument capable of analyzing single cells
as they pass through an orifice at high
velocity.
• Measures the properties of light scattering by
the cells.
• Detection by the emission of light from
flourescently labelled mAb bound to the
surface of the cell