Low white blood cell count

Does anyone here have or have had a low white blood cell count? And if you did, did it improve by treatment of your IBD?  I developed one about the time I date my illness-about 40 years ago. It was consistently either borderline or upper limits of low all that time. It was specifically the white cells known as neutrophils that was low, so the technical term was that I had a neutropenia, cause unknown. It was never low enough to affect my ability to fight infection .  In 2009, after I was first treated for IBD, it got as low as 2.2 and my NP sent me to a hematologist who did a bone marrow which was normal.  about 4-6 weeks after starting humira I had blood work done (because I was still on pentasa) and lo and behold, my WBC count was normal and still is.  Not way up there but almost 5.0 which falls in the normal range.  WTH? 

I was reading some websites on the immune system which is way over my head but I managed to get some of it.  There is a type of T helper cell called Th17. Apparently in IBD these Th17 cells draw neutrophils to the intestinal membrane.  I'm wondering if that is the reason why I had this low WBC for so long- for some reason my bone marrow did not make up for it. Maybe it kind of reached a steady state- enough WBC in my bloodstream to keep me healthy and still this pull to the intestines.  This is probably way too simple but it is puzzling why as soon as I am treated with humira my WBC becomes normal. The only other time (and I assume also when I've been fighting infection) is when my rheumatologist put me on prednisone and it went up to the mid 5,000 range, which prednisone does.

Not sure if it is helping me any because I never got sick anyway, even when my WBC went down to 2.2.  It has to go quite low before you lose your ability to fight infection.  Another weird thing is that from my reading that humira doesn't seem to act on this type of immune cell.