Plaque-forming cells in mice after experimental infection with Brucella abortus

Cells producing antibody to brucella lipopolysaccharide were detected in spleens of mice infected with Brucella abortus 19 by a hemolytic plaque assay. The appearance of immunoglobulin M-producing cells preceded humoral antibodies. The primary plaques were observed 5 days after inoculation, and they were still present by day 70.