Ok... Vitamin D regulates the immune system. Since your D3 level is in the tank, then it makes since that the IgM would be low. That is to someone who is a total lay person and just did a quick google on IgM and read up on Wikipedia *grin*!
One thing though... my level was 12 not too long ago ('bout 3-4 year) and I'd been taking 1,000iu and it did nothing. I started taking 20,000iu daily after hearing from some other folks who had really low levels and what their doctors recommended to get it up. The general consensus was 20,000iu was needed to get it up. For me, 20,000iu daily got my levels up to 54 or 56 in 'bout 3 months. You want your levels in the 70's at minimum so you begin to store reserves, which is the latest word on D3 from vitamindcouncil.org
Yah, 2000iu is not enough to get levels up from what i hear.
my levels were at 27 and im taking 10,000 iu a day to boost levels will retest in 3 months. 5000iu is maintenance from what i hear, so dont think 2000iu will do much at all.
whenever i've had tests for antibodies they've usually been low. began to wonder if it means i dont have issues or im not producing the antibodies. had the elisa foodtest done a couple of years ago which i think measures antibodies to foods, and that barely picked anything up. also the candida antibodies test a couple of months ago which picked up very low levels and i was convinced i had candida. maybe i should just take it as a good thing. I dont know if the D level is a factor in my case as 27 is not that low. it was 31 a year ago but for various reasons stopped taking the d3.
I don't know if anyone has answered your questions about this, but you should see an immunologist about the low IgM levels. This will cause you to have chronic viruses. I'm not sure if there's a treatment, but check out the herbs licorice, astragalus and echinicea.