SCID (Severe Combined Immunodeficiency Disease - Immunodeficiency Disease) mice cannot make T cells or B cells. Thus they are helpless not only to fight infection but also to reject transplanted tissue. This is due to exceedingly rare and useful spontaneous mutation on chromosome 16 responsible for deficient activity of an enzyme involved in DNA repair. Because V(D)J recombination does not occur, the humoral and cellular immune systems fail to mature. SCID mouse is therefore one of the best animal models ever found for studying the basic biology of the immune system as well as several diseases.

Omen Syndrom is a form of SCID in humans

Immunology