lab 11 -SerologyI 2021.pptx serology 2021

serology lec

1. Antigen-Antibody Reactions Lab11 (See lab Manual) General Features of Serological Tests

2. * Antigens and antibodies bind with each other specifically * In vitro , Applications of Ag- Ab reactions Diagnosis of many diseases Severity or stage of diseases Respond to treatment Epidemiology

3. Factors affecting measurement of Ag- Ab reactions * Affinity * Avidity * Ag : Ab ratio * Physical form of the antigen

4. Types of Antigen – Antibody Reactions Precipitation reaction Agglutination reaction Complement fixation test Immunofluorescence Radioimmuno assay Enzyme immunoassay

5. Precipitation reaction * The Ag is soluble , Ag- Ab complex forms an insoluble precipitate * Precipitation can take place in liquid media or in gels such as agar

6. Principle of precipitation reaction

7. * Ring test : Layering Ag solution over a column of antisera in a narrow tube * e.g. Grouping of Streptococci by Lancefield technique

8. Single Radial Immunodiffusion ( Mancini ) * Ab is incorporated into the agar gel and the Ag are placed in holes * The Ag diffuses into the gel it reacts with the Ab till the equivalence point is reached a ring of precipitation is formed Uses: 1. Determination of Igs levels 2. Complement proteins in patient samples

9. Double diffusion ( Ouchterlony ) * Ab and Ag are loaded in different wells and diffuse through the agar * When the optimal Ag- Ab ratio is reached a visible band appears in the gel.

10. Identity Non-identity Partial identity

11. Difference between Single & double immunodiffusion

12. Immuno electrophoresis

13. Agglutination Reactions * The Ag is particulate ( insoluble) * Agglutination (clump) formation occurs due to cross linking of various antigen particles by the antibody. * Qualitative & quantitative * The Titer is the maximum dilution that gives visible agglutination

14. Prozone phenomenon In an agglutination or precipitation reaction, the zone of relatively high antibody concentrations within which no reaction occurs (False negative result) . This phenomenon may be due simply to antibody excess or it may be due to blocking antibody or to nonspecific inhibitors in serum. How can overcome this phenomenon ? As the antibody concentration is lowered below the prozone . i.e. with dilution of serum sample

15. Types of Agglutination 1. Slide – Blood grouping 2. Tube – Widal test 3. Hemagglutination 4. Latex agglutination

16. Hemagglutination * Erythrocytes are coated with a soluble antigen e.g. influenza virus antigen , and use the coated RBCs in an agglutination test for Abs detection Agglutination No Agglutination No Ab

17. Latex agglutination * Inert particles (polystyrene latex, charcoal) coated with antigen or antibody

18. Applications of latex agglutination 1- Pregnancy test 2- Rheumatoid Factor Test