When I was diagnosed 7 years ago I had 3 T-cells and a viral load of 178,000, yet I felt and looked perfectly fine. Even my doctor was baffled. To date, my VL is undetectable and my T-cells are struggling at only about 70, but I'm still quite healthy. Is this common? And how is it possible?

Glad that you are doing so well. I am not surprised at all that your T-cell counts remains low, nor that you are doing clinically well despite the low CD4 count for such a long time.

It seems that before you started therapy you really had severe depletion on your nadir CD4 cells, which are the cells eventually responsible to generate more T-cells. The more immunesuppressed you were before starting therapy, the more difficult, and longer, it is going to take for those T-cells counts to increase to a safer level. Some people with similar numbers of T cell counts are never able to restore their immune function, or to gain a respectful number of CD4 T-cells despite a decade of therapy. A better way to look at your immune reconstitution will be to look at the improvement on your CD4 %, and see how close they are from reaching 14% (equivalent to 200 CD4 T-cells).

The reason why are you doing so well despite that low CD4 count is because indeed you have gained significant immune function, even with the modest improvement on your CD4 T-cell count. In addition, and probably most importantly, it is because your HIV VL is undetectable! Having an undetectable VL, in the presence of a low CD4 count, is a much predictor of a better outcome than having a few more CD 4T-cells. So, keep it up. Take your meds, maintain an undetectable VL and be patience with the further regeneration on your Cd4 cells.