This document discusses differential diagnosis of brucellosis serologic reactions. It summarizes that Brucella species differ in their primary smooth lipopolysaccharide antigens, with B. melitensis and B. abortus expressing A and M antigens, and B. suis expressing primarily A antigens. Immune response to Brucella infection involves both cell-mediated and humoral antibody responses. Common serologic assays used for brucellosis diagnosis include detection of antibodies in serum or milk through rapid and inexpensive tests, though vaccination and environmental conditions can impact test sensitivity and specificity.