For depletions in WT mice, 500 mg of lymphocyte-depleting antibody or an isotype-matched control antibody [SFR3-DR5, IgG2b] was administered i.p. one day prior and one day after infection. For depletions in adoptive transfer experiments, depleting antibodies were administered to RAG1-/-recipients as described above with one dose one day prior to splenocyte transfer and a second dose on the day of trnsfer. The efficacy of lymphocyte depletion in both sets of depletion experiments was monitored by flow cytometric analysis of splenocytes at the end of the experiment.