HUMAN PERIPHERAL-BLOOD CD4(-CELLS EXPRESS TH1-LIKE CYTOKINE MESSENGER-RNA AND PROTEINS FOLLOWING IN-VITRO STIMULATION WITH HEAT-INACTIVATEDBRUCELLA-ABORTUS() AND CD8(+) T)

Defining the pattern of lymphokine production associated with Brucella abortus is critical for advancing the development of B. abortus as a vaccine carrier. In the present study we investigated the ability of h eat-inactivated B. abortus or lipopolysaccharide from B. abortus to in duce lymphokine production from purified human T cells in vitro, Gamma interferon (IFN-gamma), interleukin-2 (IL-2), IL-4, and IL-5 inductio n was assayed by mRNA-specific PCR and by enzyme-linked immunosorbent assay and bioassay for protein production, Following depletion of mono cytes and B cells, B. abortus increased IFN-gamma and IL-2 mRNA expres sion in purified T cells compared with expression in unstimulated cell s. In contrast, no IL-5 mRNA expression and only transient low-level I L-4 mRNA expression and no IL-4 protein secretion were detected. Phyto hemagglutinin or phorbol myristate acetate plus ionomycin induced mRNA and protein for all these cytokines. Similar results were obtained wi th LPS purified from B. abortus. Removal of NK cells did not reduce ly mphokine production, and enriched NK cells did not express IFN-gamma m RNA or secrete IFN-gamma protein in response to B. abortus, indicating that NK cells were not the responding population, Both CD4(+) and CD8 (+) populations produced IFN-gamma and IL-2 in response to B. abortus. Preincubation of resting T cells with B. abortus or LPS from B. abort us for 7 days induced their differentiation into Th1-like cells as jud ged by their subsequent lymphokine response to phorbol myristate aceta te plus ionomycin. These results suggest that B. abortus con induce di fferentiation of Th0 into Th1-type cells.