immunology of infectious and parasitic diseases - XXXVII Congress ...

PHENOTYPIC AND FUNCTIONAL ANALYSIS OF CD4 + FOXP3 +
REGULATORY T CELLS (TREG) IN THE EARLY PHASE OF MURINE
INFECTION WITH TRYPANOSOMA CRUZI.
BEATRIZ VILLAS BÔAS 1 ; ROGÉRIO SILVA DO NASCIMENTO 1 ; JOSÉ M
ÁLVAREZ 1
1 Departamento de Imunologia, Instituto de Ciências Biomédicas, Universidade
de São Paulo, Brazil.
Introduction: Recently, studying TREG cells in the acute phase of infection with
T. cruzi (Y strain), we observed their numbers just marginally increase. Besides,
acute phase parasitemias and heart pathology in mice treated with monoclonal
anti-CD25 (PC61) were not different from that in animals treated with irrelevant
monoclonal antibody. These results, although not conclusive, suggest that T
cells might not be involved in the regulation of the early immune response to T.
cruzi. Using FoxP3 + GFP + mice, we have studied the phenotypic changes in the
spleen TREG population along the first weeks of infection with Sylvio X10/4 T.
cruzi parasites. Methods and Results: Spleens from FoxP3 + GFP + infected and
non-infected mice were analyzed for weight, total cell count, number and
frequency of CD4 + FoxP3 - and CD4 + FoxP3 + cells, as well as expression of
markers representative of the TREG molecular profile. Peak weight and
cellularity, as well as peak CD4 + cell numbers, were attained on the 11 th day
post-infection (d.p.i.). Along the analysis period (4 th to 18 th d.p.i.) there were no
major changes in TREG numbers, but their frequency among CD4 + cells
decreased, the percentage of CD4 + cells among total splenocytes being
minimally altered. Increased frequencies of large cells (blasts) among
CD4 + FoxP3 + and, more notably, among CD4 + FoxP3 - cells were observed.
Regarding the expression (MFI) of different markers in the TREG population, we
observed a slight increase in FoxP3 levels, a strong progressive increase in
CD25 expression that peaked at day 14 p.i., the appearance of a small CTLA-
4 HIGH population, and a late increase in GITR expression. Besides, we observed
increases in ICOS in the last days analyzed and an increased expression of Fas
(at day 11 p.i) and FasL (at days 11 to 14 p.i.). In addition, CD69 suffered a
slight persistent augment, and no changes were observed in CD127 and OX40
expression. Regarding the expression of these markers on the CD4 + FoxP3 -
population, the most relevant changes after infection were a brief small increase
in CD25, a persisting increase in Fas with presence of a small Fas HIGH subset
and no changes in FasL expression, a persisting increase in ICOS, an increase
of OX40 from 7 to 11 d.p.i., CTLA-4 increases on the 7 and 14 d.p.i. and a late
augment of GITR. Conclusion: The expression changes observed in spleen
TREG cells in the early infection by T. cruzi do not indirectly support a functional
loss in their suppressive capacity.