<prompt> Which of the follow ing is an example of heterophile antibody test-Widal testWeil-Felix reactionRose-wraler testBlood grouping cross matching  <response>: Ans. is b i.e., Weil-Felix reaction Ref: Ananthanarayan 9thep. 109 - 8the p. 108; Immunology Lachmann 4th ep. 1534. 1535Heterophilic agglutination reactiono Some organisms of different class or species share closely related antigens.o When serum containing agglutinin antibody of one organism gives agglutination reaction with antigen of other organism, it is called heterophilic agglutination test.Examples areo Streptococcus M.G agglutination test for primary atypical pneumonia,o Weil - Felix reaction for typhus fever.o Paul Bunnell test for IMN. 