Trypanosoma cruzi: the expansion of NK, T, and NKT cells in the experimental infection.

T and NK cells play a key role in resistance to Trypanosoma cruzi infections, mainly through IFN-gamma production. The expression of T and NK cells surface markers was studied in NWNA spleen cells of resistant C3H and susceptible BALB/c mice that release IFN-gamma in the early and late acute infection, respectively. In the progressively enlarged spleens, we found: (a) an increased percentage and number of NK blast cells as early as at 2 days post-infection (pi), (b) an enrichment of T and NK cells, in both the total and blast populations, during the late acute phase. At 17 days pi, there was also an accumulation of TCR- alphabeta+DX5+, NKT cells, mainly in resistant mice. At 21 days pi, the enrichment of NK cells ceased, while spleen cells and the T cell compartment continued their expansion. In the chronic stage, TCR-alphabeta+ blasts were expanded in both mouse strains, but NK blasts increased only in BALB/c that, unlike C3H mice, release IFN-gamma. As T and NK cell proliferation is not always associated to IFN-gamma release the experimental downregulation of their expansion to avoid tissue damage could be explored.