TIM 1 is a transmembrane protein containing immunoglobulin domain and mucin-like domain; it is developmentally expressed at very high levels in the blastocyst. TIM 1 binds hepatitis virus in humans and is expressed on activated CD4+ lymphocytes especially on Th2 cells and has been implicated to play a critical role in the development of atopic disease (in particular airway hyperreactivity) and other Th2-biased immune responses.