NK1.1，a member of the NKRPI family of cell surface receptors，is a type II integral membrane protein with a C type lectin domain. It is expressed as a disulfide linked homodimer on all NK cells，as well as subsets of thymocytes and peripheral T lymphocytes in selected strains of mice (e.g.，C57/BL6，FVB/N，NZB; but not A，AKR，BALB/c，CBA/J，C3H，C57BR，C58，DBA/1，DBA/2，SJL，129). NK1.1 mediates cellular activation and differentiation，and is thought to have a particular role in generating Th2 cells.