H. Qi et al., Leishmania amazonensis - Dendritic cell interactions in vitro and the priming of parasite-specific CD4(+) T cells in vivo, J IMMUNOL, 167(8), 2001, pp. 4534-4542
The progressive disease following Leishmania amazonensis infection in mice
requires functional CD4+ T cells, which are primed to a disease-promoting p
henotype during the infection. To understand how these pathogenic T cells a
re generated and the role of dendritic cells (DCs) in this process, we use
DCs of susceptible BALB/c and resistant C3H/HeJ mice to examine parasite-DC
interactions in vitro as well as the effector phenotype of T cells primed
by parasite-exposed DCs in vivo. Our results demonstrate that amastigotes a
nd metacyclics efficiently enter and activate DCs of both genetic backgroun
ds. Infection with amastigotes fails to induce CD40-depedent IL-12 producti
on, but rather potentiates IL-4 production in BALB/c DCs. Upon transfer int
o syngeneic recipients, amastigote-exposed BALB/c DCs prime parasite-specif
ic Th cells to produce significantly higher levels of IL-4 and IL-10 than t
heir C3H/HeJ counterparts. Transfer studies with IL-4(-/-) DCs indicate tha
t this enhanced Th2 priming seen in BALB/c mice is partially due to the IL-
4 production by amastigote-carrying DCs. These results suggest that L amazo
nensis amastigotes may condition DCs of a susceptible host to a state that
favors activation of pathogenic CD4(+) T cells, and thereby provide a new p
erspective on the pathogenesis of cutaneous leishmaniasis and protozoan par
asite-host interactions in general.