Tim-4 (T-cell immunoglobulin mucin 4), a transmembrane glycoprotein and member of the immunoglobulin superfamily, is exclusively expressed by antigen-presenting cells, which acts as the natural ligand of Tim-1, involved in T-cell expansion and cytokine production. Tim-4 is reported to be crucial for the phagocytosis of apoptotic cells by peritoneal macrophages, and studies have shown that interaction between Tim-1 on Th2 cells and Tim-4 on DCs, enhances Th2 cell function. The TIM-4 gene locus is associated with predisposition to asthma in both mice and humans and may be considered as a candidate disease gene for asthma. Studies have shown that Tim-4 significantly inhibits the efficient phagocytosis of apoptotic cells by PRMs (peritoneal resident Mac1+ cells), but not PEMs (peritoneal exudate Mac1+ cells) see Nakayama, M. et al. . for details.