T-Cell-Dependent Control of Acute Giardia lamblia Infections in Mice
ABSTRACTWe have studied immune mechanisms responsible for control of acuteGiardia lambliaandGiardia murisinfections in adult mice. Association of chronicG. lambliainfection with hypogammaglobulinemia and experimental infections of mice withG. murishave led to the hypothesis that antibodies are required to control these infections. We directly tested this hypothesis by infecting B-cell-deficient mice with eitherG. lambliaorG. muris. Both wild-type mice and B-cell-deficient mice eliminated the vast majority of parasites between 1 and 2 weeks postinfection withG. lamblia. G. muriswas also eliminated in both wild-type and B-cell-deficient mice. In contrast, T-cell-deficient andscidmice failed to controlG. lambliainfections, as has been shown previously forG. muris. Treatment of wild-type or B-cell-deficient mice with antibodies to CD4 also prevented elimination ofG. lamblia, confirming a role for T cells in controlling infections. By infecting mice deficient in either αβ- or γδ-T-cell receptor (TCR)-expressing T cells, we show that the αβ-TCR-expressing T cells are required to control parasites but that the γδ-TCR-expressing T cells are not. Finally, infections in mice deficient in production of gamma interferon or interleukin 4 (IL-4) and mice deficient in responding to IL-4 and IL-13 revealed that neither the Th1 nor the Th2 subset is absolutely required for protection fromG. lamblia. We conclude that a T-cell-dependent mechanism is essential for controlling acuteGiardiainfections and that this mechanism is independent of antibody and B cells.