CEACAM1 and infection: To further determine whether treatment with anti-CEACAM1 mAb acts specifically on CD8+ T cells, we transferred equal number of P14 × WT (CD45.1) splenocytes into Ceacam1–/– mice and then treated those mice with anti-CEACAM1 mAb or isotype mAb, followed by LCMV-Docile infection (Fig. 5f).