Yeah, it's a spinoff with a female white blood cell, as you see above, and a male red blood cell. "Black" refers to a "black" working environment, meaning cruel, harsh, no time for rest, and so forth. The body they're in is of some person who has many unhealthy habits, such as smoking, eating poorly, etc.
As for where to read, I've no idea. Pulled the above info off a google search.