I'm not sure that I completely understand what you've tried to ask... but my PALS did have some experience with IVIG. She was originally diagnosed with Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). This was an autoimmune deficiency wherein the body's immune system begins to attack the myelin sheath around the nerves. Just as a wire has an insulator around its core, our nerves have the myelin sheath around the nerve's axon. When it is damaged (i.e. the immune system becomes confused and begins to munch on its own nerves), the signals that run from spinal motor neuron, through the nerve path to the muscle begin to lose signal strength. As a result, muscles don't move as well as they did previously. If the "munching" continues unabated, the axon itself can be severed. When that happens, the signal may no longer get to the muscle at all.
IVIG treatments infuse good immunoglobulins into the body. The expectation is that the confused immunoglobulins will say, "Hey look! Reinforcements have arrived. We can stand down now and let them do the work!" Eventually, the hope is that all of the "nerve munching" ceases and the nerves can begin to heal. Though a slow process, axons can regrow and reconnect... and the myelin sheath can rebuild.
My wife was on IVIG treatments for a year. During the last 3 or 4 months of that year, she was on a 4x dosing (spread over 4 days). At no time did her symptoms lessen, her decline halt or did she feel better from the treatment. After a year of continued decline and a doctor who was adamant that she did not have ALS (even after indications of motor neuron disengagement), we asked to be referred to Johns Hopkins for an alternate opinion. It was there that she was diagnosed with MND/ALS and the IVIG was exchanged for Riluzole.
I don't know if that helps any... but I hope you find the answers that you're looking for...
Jim