Why is it that we can treat this disease with immunosuppressants which causes our kids to be susceptible to getting sick which in return can cause flare ups when they get sick?
This is a great question. In fact we try to avoid immunosuppressants whenever possible. Most of the common first line disease modifying therapies (DMTs) are immunomodulators that alter specific inflammatory responses without globally suppressing the immune system.
All the interferons and Copaxone are examples of immunomodulators; these DMTs do not increase the risk of infection and interferons may even decrease the risk common viral infections. Aubagio rarely increases the risk of infection since lymphocytes are able to use the "salvage pathway" to proliferate (reproduce). Other drugs like Tysabri and Gilenya have powerful but selective effects on the immune system and minimally increase the risk of common infections, although certain very rare infections (like PML) can have devastating consequences if not detected early. Both Tysabri and Gilenya can increase the risk of shingles as well. Shingles, as you know, is a reactivation of a dormant infection with varicella, the virus that causes Chickenpox. Tecfidera does have minimal suppressive effects on certain lymphocytes, particularly CD8 positive lymphocytes, and may increase the risk of infections if the lymphocyte count drops too low. This is the reason for monitoring lymphocyte counts in patients on Tecfidera. Rituximab selectively targets and destroys B lymphocytes expressing CD20 but this effect rarely lowers immunoglobulin levels or increases the risk of common infections.
Certain DMTs used to treat MS clearly are immunosuppressive and significantly increase the risk of infection; these include alemtuzumab (Lemtrada), cyclophosphamide and chronic corticosteroids. Of all these treatments, it is rare for anyone to be treated with chronic corticosteroids these days as the risks outweigh the benefits in most circumstances.
Generally, MS specialists recommend those treatments with the fewest suppressant effects on the immune system as first line therapies to avoid infections and only escalate treatment to those drugs that can significantly suppress the immune system when the potential benefits outweigh the risks.
Revere (Rip) Kinkel MD
Director of the UCSD Multiple Sclerosis Program