T-CELL RECEPTOR V-BETA REPERTOIRE IN THE THYMUS AND SPLEEN OF MICE INFECTED WITH TRYPANOSOMA-CRUZI

The T cell receptor (TCR) V beta repertoire was studied in BALB/c, CBA /HJ, and CBA/J mice experimentally infected with Trypanosoma cruzi. Th e percentage of expression of 14 V beta chains of the variable domain of the TCR in the thymus and spleen was evaluated. In the thymus of ac utely infected BALB/c and CBA/HJ mice there was an increase in the exp ression of positively selected V beta chains, without modifications in the negatively selected V beta families. These changes in the V beta chains usage in the thymus paralleled the enrichment of CD4(+) and CD8 (+) single-positive T cells. During the acute infection, several chang es were observed in the peripheral expression of V beta families, such as of V beta 6 in BALB/c (a 36% increase in CD8(+) T cells of the cor responding levels of V beta), of V beta 8 in CBA/HJ (a 37% decrease in CD8(+) cells), and of V beta chains 8 and 14 in CBA/J mice (V beta 14 (+)CD4(+) cells increased 19%, and V beta 8 expression decreased 19 an d 33% in CD4(+) and CD8(+) cells, respectively). In chronically infect ed BALB/c and CBA/HJ mice, no change in the V beta families was observ ed, neither in the thymus nor in the spleen. In acutely infected mice, the alterations of the peripheral expression of positively selected V beta families could be due to the stimulation by T. cruzi antigens an d/or cytokines; the homeostatic mechanism/s that maintains the selecti on of the TCR V beta repertoire did not seem to be severely affected d uring the infections. (C) 1996 Academic Press, Inc.