A genetic locus and corresponding family of proteins associated with regulation of immune function and cell survival are provided. These genes encode cell surface molecules with conserved IgV and mucin domains. The locus comprising the TIM family is genetically associated with immune dysfunction, including asthma. Furthermore, the TIM gene family is located within a region of human chromosome 5 that is commonly deleted in malignancies and myelodysplastic syndrome. Polymorphisms in the gene sequences are associated with the development of airway hyperreactivity and allergic inflammation, and T cell production of IL-4 and IL-13. The proteins include the human hepatitis A cellular receptor, hHAVcr-1.