I found an interesting article, but there's a lot of medical-speak in the conclusions I can't fathom. If anyone feels like translating, I'd love to hear it!

ISSUES IN NUTRITION – including Home-Made and Raw Food Diets by W. Jean Dodds, DVM
http://64.233.179.104/search?q=cache:RpZVCQQuNiIJ:www.homevet.com/petcare/documents/immunenutrition.pdf+dog+home+made+quinoa&hl=en

Lisa, I worked in a Pedi office for 7 years.....I tried. But it was a little over my head. Sorry.

This is what I got out of it.

Nutrition and the Immune System
A complete diet is required for a healthy immune system. Diets deficient in zinc, selenium and vitamin E, vitamin B-6 (pyridoxine), and linoleic acid negatively impact both parts of the immune system (humoral and cell-mediated). It's also difficult to decide what is the appropriate amount of vitamins for each individual dog because of lifestyle and genetic variations. The humoral system is the immunity provided by antibodies (proteins). Cell-mediated immunity comes from T-cells or other lymphocytes.

Nutrition and Thyroid Metabolism
Zinc and iron are neaded for healthy thyroid metabolism. Although supplemented in commercial foods, it is difficult to determine the ideal amounts for each breed. Thyroid hormones in the blood rise when the body is deficient in selenium. Synthetic antioxidants can impair the absorption of Vitamin A, E, and selenium. Thyroid dysfunctions lead to a poor immune system.

Nutritional Management (Commercial, Home-Made and Raw Food Diets)
Increasing carbohydrates, decreasing proteins, and using high quality proteins may help dogs suffering from immunological disorders. Elimination diets are also beneficial. Grains, except for quinoa, sorghum, barley, and/or flax, are often avoided. There isn't conclusive evidence to show that high protein diets (BARF) cause, or do not cause, kidney problems. Vitamin A and E aid the immune system as well as lutein and beta-carotene in dogs, but not cats.

Raw Food Diet Study
87 dogs were fed Billinghurst diet, 46 the Volhard diet, and 94 were fed various custom raw diets. As compared with dogs eating a cereal-based diet the raw dogs had more red blood cells (or larger red blood cells), more nitrogen waste in their blood, and more creatine by-products in the blood.