1. mice, scid Mice homozygous for the mutant autosomal recessivegene "scid" which is located on the centromeric end of chromosome 16. These mice lack mature, functional lymphocytes and are thus highly susceptible to lethal opportunistic infections if not chronically treated with antibiotics. The lack of B- and T-cellimmunity resembles severe combined immunodeficiency (SCID) syndrome in human infants. SCID mice are useful as animal models since they are receptive to implantation of a humanimmunesystem producing SCID-human (SCID-hu) hematochimeric mice.