I get IVIG infusions every 4 weeks for my CVID. IVIG is a blood product that has some immunoglobulin components that I don't make myself. Those components are the IgA, IgD, IgE, IgG and IgM, though IVIG doesn't have them all. IVIG can also be used to raise the platelet count from idiopathic thrombocytopenic purpura (ITP). Works great for me for both. You're not really boosting the immune system with it, but rather you're boosting the components that identify invaders to the body's systems, which allows the rest of the immune system to function better. The immunoglobulin components are what "bind" to the "invaders" to identify them as such. What's weird for me, is that having a compromised immune system, you'd think that there wouldn't be any AI inflammatory issues, but au contraire... Low immunoglobulin counts lets all manner of "baddies" to run rampant in your system. Since I've been on IVIG regularly (two years now), my incidence of contracting pneumonia has decreased (been over a year now since I've had it), and I don't arbitrarily get bronchitis everytime I catch a cold. It also "smooths out" the lupus somehow. The brain fog isn't nearly as bad, isn't constantly there, and only gets really bad during flares now (which still happens). IVIG doesn't "cure", doesn't eliminate symptoms, but it does help my body "fight the good fight".
Some of its disadvantages are possible allergic reactions, headache, etc., from the actual infusion, and then there's the problem of it skewing future blood work results, since you're artificially raising several levels in your blood. You also increase the risk of contracting blood-borne illnesses, but they screen donors better today, and the product is also "filtered". There is also the issue of cost. It usually run in the neighborhood of 10k-18.5k US dollars per treatment, dependant upon the situation, so insurance can really be an issue. It's definitely something to really discuss with all your doctors, and not just the one prescribing it.
"There but for the grace of God, go I."
"... His mercy endureth for ever."