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Infect. Immun., Jan 1997, 42-48, Vol 65, No. 1
PS Coulson and RA Wilson
The effector mechanism, which operates against challenge parasites in the
lungs of C57BL/6 mice vaccinated once with irradiated cercariae of
Schistosoma mansoni, is mediated by CD4+ T helper lymphocytes. However,
adoptive transfer of immunity from vaccinated donors to naive recipients by
using sensitized T cells has not proved successful. One explanation may be
that the recruitment of sensitized T lymphocytes to the lungs by
vaccinating parasites to arm that organ is not reproduced by transfer
protocols. We have used the technique of parabiosis, as a means of adoptive
transfer, to demonstrate the relevance of pulmonary T cells to protection.
Sensitized and naive partners were joined surgically for a 28-day period,
coincident with priming of the immune system. A vascular union rapidly
developed, and sensitized T cells were detected in the spleens of the naive
partners. When parabionts were challenged percutaneously 10 days after
separation, the level of immunity transferred to the naive partners was
approximately two-thirds that of their vaccinated counterparts. The naive
partners, unlike the vaccinated animals, did not recruit lymphocytes to the
lungs during the priming period. In contrast, after percutaneous challenge,
schistosome- specific lymphocytes were recruited to the lungs of both
separated parabionts. The importance of lymphocytes recruited to the lungs
during the primary response was revealed by an intravenous challenge with
lung schistosomula; this eliminates the opportunity for secondary immune
responses prior to parasite arrival in the lungs. In this situation, the
vaccinated partners showed 47% immunity while the naive partners were not
protected. We conclude that the presence of specific T cells in the lungs
at the time of challenge confers a significant advantage, permitting a more
effective recall response than in animals lacking such resident cells.
Copyright © 1997, American Society for Microbiology
Recruitment of lymphocytes to the lung through vaccination enhances the immunity of mice exposed to irradiated schistosomes
Department of Biology, The University of York, United Kingdom. PSC3@york.ac.uk
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