Whole-blood lymphocyte stimulation assay for measurement of cell-mediated immune responses in bovine brucellosis

Abstract

A study was conducted to develop an in vitro whole-blood lymphocyte stimulation assay for measurement of cell-mediated immune response in bovine brucellosis. A soluble antigen (BASA) prepared from killed cells of Brucella abortus 1119-3 was used. Cattle infected with B. abortus field strains, B. abortus 19 calfhood- and adult-vaccinated cattle, and nonexposed cattle were tested. Blood was diluted 10-fold in RPMI-1640 medium (without added serum) and cultured with BASA (at a concentration of 2.2 .mu.g/culture) at varying times of incubation. [3H]thymidine incorporation into DNA was assayed. A 6-day period was optimal for incubating blood cultures to achieve maximum specific lymphocyte stimulation. Serological tests and bacteriological isolation attempts were conducted simultaneously with lymphocyte stimulation tests, and there was a significant correlation between cell-mediated immune response and bacteriological findings. There was a significant correlation between cell-mediated immune response and the level of serum antibodies on a group basis, but there was little correlation between the 2 systems on individual infected animals. Among vaccinated animals there was little or no correlation between cell-mediated immune and humoral responses. The whole-blood assay was simple, fast, sensitive and reproducible.