Weil felix reaction is -

Ans. is 'd' i.e., Tube agglutination test Precipitationo When a soluble antigen combines with its antibody in the presence of electrolytes (NaCl) at a suitable temperature and pH, the antigen - antibody complex forms an insoluble precipitateo When instead of sedimenting, the precipitate remains suspended as floccules, the reaction is known as flocculation.o It is very sensitive in detection of antigens and as little as 1 g of protein can be detected by precipitation testso Precipitation is relatively less sensitive for the detection of antibodies. Precipitation / flocculation tests | |||||Ring testslide testTube test (Precipitation in gel)ImmunodiffusionElectroimmuno diffusiono Ascoli's thermoprecipitation test for Bacillus anthraxo Grouping of streptococci by the lancefield techniqueoVDRL (flocculation test) for syphiliso Kahn test (flocculation test for syphilis) for detection of alpha- fetoprotein in serum and cryptococcal antigen in the C.S.F.o Elek test for toxigenicity in diphtheria bacillio Most important is countercurrent immunoelectrophoresisAgglutinationo When a particulate antigen is mixed with its antibody in the presence of electrolytes at a suitable temperature and pH, the particles are clumped or agglutinatedo Agglutination is more sensitive than precipitation for the detection of antibodies.Agglutination tests|||||Slide agglutinationTube agglutinationCoombs testPassive agglutination testo Blood grouping and cross - matchingo Widal testo Weil - felix reactiono Paul Bunnell testo Cold agglutination testo Streptococcus MG agglutination testo Anti - Rh antibody test||||| Haemagglutinationo Rose Waaler test for R. A.Latex agglutinationo Detection of: ASO CRP RA factor HOGComplement fixation testo The ability of antigen antibody complexes to 'fix' complement is made use of in the complement fixation testo This is very sensitive test, capable of detecting 0.04 mg of antibody nitrogen and 0.1 mg of antigeno The source of complement is guinea pig serumo Examples# Wassermann CFT for syphilis# Treponema pallidum immobilization test.Antigen - antibody reaction||||Soluble antigenParticulate antigenAntigen+++AntibodyAntibodyAntibody+++ElectrolyteElectrolyteSource of complement|||PrecipitationAgglutinationComplement fixation test