Can someone explain to me why so many very sick, immune compromised people wirh candida, and probably other infections have almost always normal blood count?

I mean these things happen: candida grows, other bacteria viruses spread but there is no immune response.

WHY?

I dont't remember well but wasn't there somewhere a theory that mercury makes the immune system 'blind' to all those pathogens? If so, how? Are there any studies, and theories out there that explain this? Is there some explanation?

I think it's quite crucial to wonder why this the way it is because normal blood count is usually the basis for doctors to ignore things.