Characterization of a naturally occurring severe combined immunodeficiency in pigs (P6087)

Abstract

Abstract Severe combined immunodeficiency (SCID) refers to a group of inherited disorders in which two components of the immune system are defective. We have identified a naturally occurring, SCID in a line of pigs that were bred for increased feed efficiency. Affected piglets remain healthy while on the sow, but succumb to infections soon after weaning. SCID piglets have underdeveloped lymph nodes and spleen with a paucity of lymphocytes, they do not make antibodies to Porcine Reproductive and Respiratory Syndrome (PRRS) virus, and they accept human tumors. Further analyses showed that the defect has an autosomal recessive inheritance pattern. Blood was collected within 2 days after birth to titer serum immunoglobulins, perform lymphocyte counts and identify lymphocyte populations by flow cytometry. Affected piglets had no detectable serum immunoglobulins, and very low numbers of circulating lymphocytes. By flow cytometry, there were Natural Killer cells, but few to no T or B lymphocytes. At necropsy, thymus and small intestine were collected from each affected piglet and from control littermates. Histologic sections, stained with Hematoxylin and Eosin, were evaluated for cellularity. Affected piglet thymic remnants were small, containing Hassall’s corpuscles, but relatively few thymocyte-like cells. There were no detectable Peyer’s Patches in small intestine. These observations are consistent with T-/B- NK+ SCID.