The TAPR locus containing the TIM gene family is implicated in the development of atopic inflammation in mouse, and TIM-1 allelic variation has been associated with the incidence of atopy in human patient populations. In this study, we show that manipulation of the TIM-1 pathway influences airway inflammation and pathology. Anti-TIM-1 mAbs recognizing distinct epitopes differentially modulated OVA-induced lung inflammation in the mouse. The epitopes recognized by these Abs were mapped, revealing that mAbs to both the IgV and stalk domains of TIM-1 have therapeutic activity. Unexpectedly, mAbs recognizing unique epitopes spanning exon 4 of the mucin/stalk domains exacerbated immune responses. Using Ag recall response studies, we demonstrate that the TIM-1 pathway acts primarily by modulating the production of T H 2 cytokines. Furthermore, ex vivo cellular experiments indicate that TIM-1 activity controls CD4+ T cell activity. These studies validate the genetic hypothesis that the TIM-1 locus is linked to the development of atopic disease and suggest novel therapeutic strategies for targeting asthma and other atopic disorders.