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. The 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 acutely infected BALB/c and CBA/HJ mice there was an increase in the expression 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 changes 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 corresponding 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 and 33% in CD4(+) and CD8(+) cells, respectively). In chronically infected BALB/c and CBA/HJ mice, no change in the V beta families was observed, 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 and/or cytokines; the homeostatic mechanism/s that maintains the selection of the TCR V beta repertoire did not seem to be severely affected during the infections. (C) 1996 Academic Press, Inc.