Today at Maggie’s clinic visit we got the news that she is CMV Negative. This very likely means that her adaptive immune system is now back online and clearing viruses. Full celebration pending official count of CD4 cells.

Here’s my mental model of why I’m so excited.

Before Maggie even started her pre-transplant work-up, more than 4 months ago, she was a known carrier for CMV (a very common, usually non-noteworthy virus). During the transplant process, the immune system is almost entirely eliminated. Unsurprisingly, with nothing on board to fight bugs, the CMV reactivated, and she became viremic (active virus detectable in the body) for CMV. To keep the virus at bay, anti-viral medications were used in lieu of the normal immune system. This mostly worked to keep her stable, but the viremia persisted. Anti-viral drugs can’t fully eliminate CMV, so it hangs around persistently.

Fighting a virus such as CMV is one of the most complicated things that the immune system does. It requires a type of cell called a CD4, T-cell, which is a type of lymphocyte, which is a type of white blood cell. Those are the cells that go to the thalamus, and get trained to look for foreign viruses and run around killing them. This is a component of what’s known as the adaptive immune system.

The fact that she is now CMV negative, meaning no detectable virus, suggests that she has active, working CD4 cells. Phew, long explanation. Anyway, I’m happy about it.