Equine infectious anemia: activity of liquid antigen extracts in the agar-gel immunodiffusion and complement-fixation tests.

Twenty-nine lots of acetone-ether extracted liquid antigen were prepared from the pulp of 11 spleens collected from horses at the acute phase of experimental infection. The lots prepared from the highly reactive pulp resulted in general in a liquid antigen of greater activity than those extracted from weakly reactive pulps. Some variations in activity between lots of antigen prepared from the same spleen were also observed. No matter what the results, given a wide enough variation, all results were reproducible. The procedure permitted production of a greater number of antigen test doses from reactive spleens and rendered usable the spleens which failed to give sufficient reactivity when used as pulp antigen in the agar-gel immunodiffusion test. The activity of each lot of liquid antigen was standardized, first by the complement-fixation test and finally by matching with a reference antiserum in the agar-gel immunodiffusion test.