Comparison of sensitivity and specificity of purified lymphocyte and whole-blood in vitro lymphocyte stimulation assays in detection of Brucella abortus infection in cattle

A study was conducted to compare the sensitivity and specificity of purified lymphocyte and whole-blood in vitro lymphocyte stimulation assays in detection of Brucella abortus infection in cattle. Cattle used were infected with B. abortus field strains or strain 19. Peripheral blood was collected, and lymphocytes for the purified lymphocyte stimulation assay were prepared by the Ficoll-diatrizoate technique. The blood for the whole-blood lymphocyte stimulation assay was diluted 10-fold with RPMI 1640 medium (without additional serum supplement) and cultured. The two tests were run simultaneously, and B. abortus soluble antigen or concanavalin A was added to the cultures. The cultures were incubated for 6 days and assayed for [³H]thymidine incorporation into their DNA. Generally, cultures of the purified lymphocyte stimulation assay had higher counts per minute than those of the whole-blood lymphocyte stimulation assay, but the stimulation ratios for the two tests were comparable. The two assays were comparable in terms of their sensitivity and specificity as applied to detection of brucella infection in cattle.