T Cell Receptor Vβ Repertoire in the Thymus and Spleen of Mice Infected withTrypanosoma cruzi

The T cell receptor (TCR) Vβ repertoire was studied in BALB/c, CBA/HJ, and CBA/J mice experimentally infected withTrypanosoma cruzi.The percentage of expression of 14 Vβ 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 Vβ chains, without modifications in the negatively selected Vβ families. These changes in the Vβ 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 Vβ families, such as of Vβ6 in BALB/c (a 36% increase in CD8+T cells of the corresponding levels of Vβ), of Vβ8 in CBA/HJ (a 37% decrease in CD8+cells), and of Vβ chains 8 and 14 in CBA/J mice (Vβ14+CD4+cells increased 19%, and Vβ8 expression decreased 19 and 33% in CD4+and CD8+cells, respectively). In chronically infected BALB/c and CBA/HJ mice, no change in the Vβ families was observed, neither in the thymus nor in the spleen. In acutely infected mice, the alterations of the peripheral expression of positively selected Vβ families could be due to the stimulation byT. cruziantigens and/or cytokines; the homeostatic mechanism/s that maintains the selection of the TCR Vβ repertoire did not seem to be severely affected during the infections.