As suppressor of binding between selectin binding sugar chain and selectin or cell killing agent, (1) siRNA suppressing expression of genes which relates to cell surface antigen CD43 and selectin ligand sugar chain by RNA interference; (2) an inhibitor of sugar chain synthesis such as analogue of substrates in sugar chain synthesis; (3) an enzyme severing cell surface antigen CD43 and selectin ligand sugar chain; and (4) antibodies of cell surface antigen CD43 and selectin ligand sugar chain are used to selectin ligand sugar chain expressed in cell surface antigen CD43 to provide a suppressor of infiltration which is able to suppression of infiltration to tissues by leukocytes and a method of suppression thereof, and a cell killing agent of CD43 expressing cell and a cell killing method thereof.