Identifying defects in canine nucleotide salvage pathways and compositions and methods for improving immune function in dogs

A method of treating a dog diagnosed with or suspected of having immune dysfunction comprising:

• identifying the dog as a dog diagnosed with or suspected of having immune dysfunction;
• identifying the dog as having a defect or deficiency in nucleic base salvage by analyzing a biological sample obtained from the dog for the presence of 2 copies of major allele G for single nucleotide polymorphism Affx-205876096;
• and identifying the dog as having the defect or deficiency in nucleic base salvage by the presence of 2 copies of major allele G for single nucleotide polymorphism Affx-205876096, and
• administering to the dog a complete nutritional diet that comprises a therapeutic level of nucleotides, wherein the complete nutritional diet is a complete and balanced nutritional dog food that comprises 0.055-0.075% nucleotides on a dry matter basis when the dog is identified as diagnosed with or suspected of having the immune dysfunction or identified as having the defect or deficiency in nucleic base salvage.