Hi Keith,
Intravenous immunoglobulins are for when your immune system isn't producing enough of them. As you know, when that happens you are more likely to get an infection or catch whatever's going around.
Your onc will be able to advise you whether you have a reasonable amount of usable immunoglobulin or whether it's very suppressed. Levels can drop due to the myeloma itself or as a consequence of treaments.
Best,
Eva