> Now that I'm back on it, it's like somebody turned on the vitamin D
> spigot again.  The results have been so dramatic it prompted me to dig
> deeper.  It turns out regulatory T-cells have folic acid receptors [PMID
> 17613255] and certain autoimmune patients and low-functioning autistics
> [PMID 18461502] generate autoantibodies against folic acid receptors -
> quite possibly as the aftereffect of clearing out a viral infection or a
> cancer that trained B-cells to target the receptor.

> If these folic acid receptor antibodies are numerous enough, they can
> block entry of folic acid into the central nervous system.  The receptor
> is necessary for folic acid to cross the blood-brain barrier.  A patient
> with normal serum folic acid levels might actually be deficient in the
> CNS which would only show up in a tap - a procedure doctors rarely
> perform.

> It also turns out that low folic acid levels lead to higher vitamin D3
> catabolism [PMID 19450178] so if the CNS is deficient in folic acid,
> vitamin D3 isn't going to function properly - leading to a drop in redox
> capacity (e.g., low glutathione)/metals detoxification/neurogenesis,
> loss of antiviral functions/cathelicidin, increased cancer risk and
> probably autoimmune issues as well.  But it's going to be invisible to
> anybody checking strict serum levels.  It makes me wonder if certain
> vital infections don't deliberately stir up anti-folic acid receptor
> antibodies to block the antiviral effects of vitamin D3 within the
> nervous system itself.

> The upside, though, is that supplementing with folinic acid shots or a
> high dose oral folic acid seems to restore CNS levels [PMID 19260931].  
> Folic acid per se may stimulate Tregs even if patients don't have a
> deficiency (which probably accounts for why tumors use folic acid and
> are vulnerable to these antibodies).  This may mean folic acid is a good
> general treatment for autoimmune disorders.

> Serum folic acid in general can be affected by autoimmune diseases.  In
> Celiac disease, the levels of transglutaminase antibodies seem inversely
> correlated to serum folic acid levels [PMID 15861017, 17190764].  Given
> how a serum drop would affect body-wide vitamin D3 levels and the
> chemopreventative role of D3, this may be one reason bowel cancer risk
> goes up in some of these autoimmune diseases.  Since estrogen helps
> stimulate expression of the VDR, this may be a set of factors explaining
> why bowel cancer is more common in men [PMID 19450178].

> These folate receptor antibodies may be a cause of subfertility risk in
> women [PMID 18950755].  They have been associated with high milk
> consumption [PMID 19282368] and a milk-free diet can help reduce the
> autoantibodies [PMID 18355335].  Given the role opioids play regulating
> antibody production in B-cells [PMID 18387505], I have to wonder if this
> cross-reaction to folate receptors caused by consuming cow's milk might
> stem from the molecular similarities between the casein in milk and
> opioids.

> Given that my folinic acid supply will be sporadic for a while, does
> anybody know where I can find an inexpensive, high dose folate
> supplement - somewhere on the order of 10mg a day?