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
Pantethine: Boost Your Brain, Cardio Health, Metabolism, and Detoxification
by Byron Richards, Wellness Resources, February 29, 2012
B9 Folic Acid
PABA Para-Aminobenzoic Acid