[Serological diagnosis of IBR. Passive hemagglutination microreaction].

The preparation and standardization of the ingredients for PHA is described in detail. Formalin treated erythrocites in a 10% concentration treated with 1:20 000 tannin were used. The antigen concentrated by ultracentrifugation properly sensibilizes the erythrocites and their titer does not change in case of its dilution up to 1:8. The non-concentrated virus antigen has a low covering potential only if it is either not diluted, or in a 1:2 dilution and sensibilizes the erythrocites to a lesser extent. The great advantage of the use of concentrated antigen is that it equalizes antigens obtained from various lots. The optimal time for loading by erythrocites is 1 h, and a longer sensibilization has no influence on the effect of loading. It was proven that the sensibilization of formalin treated erythrocites allows long storage of the produced antigen. The tannin treated formalinized erythrocites can be stored up to 20 days without any change in their ability to be antigen covered, while the sensibilized erythrocites are not changed for 6 days and up to the 30th day their titer is twice lower, but this is of no practical importance.