Tests are still being performed, but early results are promising: baking soda appears to do a pretty good job fighting autoimmune disease.
A study in the forthcoming issue of the Journal of Immunology reports that macrophage polarisation in the spleens of human and rodent test subjects shifted from inflammatory to regulatory when the subjects had a small amount (in humans relative to a U.S. teaspoon, in the rats a rat-sized equivalency) of baking soda per day.
Furthermore, the study reports that "FOXP3+CD4+ T-lymphocytes increased in the spleen, blood, and kidneys of [the] rats." Which is a very, very fancy way of saying that baking soda increased T cells counts in the rodents. Which is pretty cool.
This section of the published study gives you a general idea of what the baking soda actually does inside of you:
Thin collagenous connections lined by mesothelial cells were found to connect to the capsular mesothelium. Mesothelial cells in these connections stained positive for the pan-neuronal marker PGP9.5 and acetylcholine esterase and contained many ultrastructural elements, which visually resembled neuronal structures. ... Our data indicate that oral NaHCO3 activates a splenic anti-inflammatory pathway and provides evidence that the signals that mediate this response are transmitted to the spleen via a novel neuronal-like function of mesothelial cells.
It might not be a great idea to chug a whole box of Arm & Hammer, but a small daily dose could do wonders for keeping your autoimmune system in check. Between that and a healthy diet of nuts, vegetables, and fish... you could have the spleen of a person half your age! Which is a good pick-up line if you find yourself at a party with a hematologist (which is a spleen doctor, in case you're wondering).
And besides, you probably have a carton of the stuff laying around somewhere. It's practically mandatory whenever you move into an apartment in a city as it helps keep odors out. So if you want to prevent autoimmune diseases and not have a stinky salad, get yourself a box.