A Severe Combined Immunodeficient (SCID) Yorkshire pig line has been identified at Iowa State University. Since SCID animals lack an adaptive immune system they are instrumental models for biomedical and immunological research. An important goal for this thesis and for development of the ISU SCID pig is to characterize its natural immune parameters, and use the SCID pig as a biomedical model for exploring research questions.

To establish a SCID colony that can reliably and efficiently produce SCID animals, bone marrow transplantations were performed to create immune-competent, genetically SCID, breeding animals. Interestingly, three of these BMT pigs were diagnosed with cancer; two with lymphoma, one with additional leukemia, and a nephroblastoma. This suggests the SCID pig may be interesting as a cancer model. Another major component in developing the SCID colony was the creation of the “bubble” facilities and associated protocols. Two bubbles were designed to limit the exposure of SCID piglets to opportunistic pathogens. This facilitates the production of specific pathogen free (SPF) SCID piglets and non-SCID littermates for further characterization and model development for use in immunological and biomedical research.

The SCID pig lacks T and B lymphocytes but has Natural Killer (NK) cells present. The functionality of NK cells has important implications for engraftment success for SCID patients and the extent of immunity present in the animal. It was important to determine the functionality of the SCID porcine NK cell. We found SCID NK cells could be activated to lyse tumor target cells (cytotoxicity) in vitro when activated with stimulating cytokines, and are capable of producing IFN- and intracellular perforin. We concluded that intrinsically, SCID NK cells are functional in vitro.

Research has established murine NK cells can exhibit memory-like behavior. Methods illustrating specific, long-lived memory responses include hapten-induced contact hypersensitivity (CHS). To establish CHS responses exist in swine, commercial pigs were sensitized on the back and re-challenged by ear injection with hapten and control combinations. CHS responses, measured as hapten specific ear swelling, showed hapten specific memory exists in the swine model, and consistent with the mouse literature, was associated with increased activation of hepatic NK cell.