The role of the thymus in modulating gammadelta T cell suppressor activity during experimental Trypanosoma cruzi infection |
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Authors: | Cardillo F; Nomizo A; Mengel J |
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Institution: | Department of Immunology, Institute of Biological Sciences, University of Sao Paulo, SP, Brazil. |
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Abstract: | We have previously shown that splenic gammadelta T cells from young but not
aged BALB/c mice possess suppressor activity in vivo and in vitro during
the acute phase of Trypanosoma cruzi infection. The present work was
undertaken to investigate the suppressor activity of gammadelta T cells
from T. cruzi-infected euthymic or athymic mice and the role of the thymus
in modulating non-adherent spleen cell suppressor activity during the acute
phase of infection. Splenic gammadelta T cells from aged or athymic BALB/c
mice reconstituted with total spleen cells or non-reconstituted did not
exhibit suppressor activity when added to full allogeneic, mixed lymphocyte
cultures. In contrast, splenic gammadelta T cells from young euthymic
BALB/c mice showed suppressor activity in vitro. Thymectomy reduced the
splenic gammadelta T cell suppressor activity of young BALB/c mice in a
time-dependent manner, following a T. cruzi challenge. The continuous
provision of thymocytes to aged mice, young thymectomized mice or total
spleen cell- reconstituted athymic mice could re-establish the gammadelta T
cell suppressor activity. Of particular significance was the observation
that the depletion of gammadelta T cells during the acute phase of T. cruzi
infection restored the capacity of these mice to mount a humoral immune
response to a non-related antigen such as ovalbumin. These results indicate
that gammadelta T cells of extrathymic origin cannot mediate suppression
and that the thymus has a role in the regulation of suppression during the
acute phase of T. cruzi infection.
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