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Infect. Immun., 03 1995, 969-975, Vol 63, No. 3
Y Zhan, A Kelso and C Cheers
In order to induce acquired cellular resistance to facultative bacterial
pathogens, infection with live organisms is required. We have previously
demonstrated that spleen cells from Brucella-infected mice produced gamma
interferon (IFN-gamma) and interleukin-2 (IL-2) in response to Brucella
antigens in vitro, while spleen cells from mice immunized with soluble
Brucella proteins (SBP) produced substantial amounts of IL-2 but no
detectable amount of IFN-gamma. In this study, we further analyzed the
response of T cells from Brucella-infected mice and SBP-immunized mice and
demonstrated that CD4(+)-enriched cells from SBP-immunized mice also
produced significant amounts of IL-4, which was not detected in bulk
cultures of spleen cells from infected mice. Limiting dilution analysis
showed that infection resulted in a higher precursor frequency of
IFN-gamma-producing CD4+ T cells and a lower precursor frequency of
IL-4-producing CD4+ T cells, while immunization with SBP resulted in a
higher precursor frequency of IL-4-producing cells and a very low frequency
of IFN-gamma-producing cells. The precursor frequencies of IL-2-producing
cells for the two groups were similar. Furthermore, IFN-gamma-producing
CD4+ T cells from infected donor mice were capable of mediating resistance
against challenge infection in recipient mice, but IL-4-producing CD4+ T
cells from immunized mice failed to do so. These results indicate that the
form of antigen has a profound influence on the outcome of the immune
response. The results are discussed in light of the supposed dichotomy
between Th1 and Th2 cytokine responses.
Copyright © 1995, American Society for Microbiology
Differential activation of Brucella-reactive CD4+ T cells by Brucella infection or immunization with antigenic extracts
Department of Microbiology, University of Melbourne, Parkville, Victoria, Australia.
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