I will be adding links suggesting the relationship between B vitamin metabolism, chronic fatigue syndrome, and chemical sensitivities.
I do not know if the immune system interferes with B metabolism, but the following article contains other interesting points:
B Vitamin Metabolism Goes Wrong
March 22, 2010 by ImmuneMatrix LLC
Lyme Disease and
by Melody O'Beau
The author has a mitochondrial disease involving B1 deficiency. Information on functional B1 testing.
Also: nicotinic acid, niacinamide, NADH
Chronic Niacin Deficiency Be a Root Cause of Increase in “Deranged”
Dr. Andrew Saul interviewed at Mercola.com
B5 Pantothenic Acid
Boost Your Brain, Cardio Health, Metabolism, and Detoxification
by Byron Richards, Wellness Resources, February 29, 2012
B9 Folic Acid
PABA Para-Aminobenzoic Acid