Ok, I will never post another biology question to yahoo answers. I'm watching Carl Sagan's Cosmos for the billionth and billionth time, and suddenly something other than stars got my attention: lymphocytes. I watched them destroying bacteria and I wondered: do they just destroy the bacteria, or do they actually eat and digest them? I mean does a lymphocyte use its prey's remains for food? Or does the corpse just become waste in the bloodstream to be removed by the kidneys or whatever? And if so, then what do lymphocytes eat? I mean, how do they get their power? For that matter, how do red blood cells get their power? They deliver fuel to the other cells of the body, right? But how do they get their own fuel? And where from? The intestine, I guess? And then, where do lymphocytes go when they're not on duty? I think I read that the NKs are just running around loose all the time, but I think that the small lymphocytes have to be activated somehow. Does that just mean that they're everywhere, sleeping until some signal travels through the body? Or do they live in a central location? I've heard hypotheses that propose that a huge fraction of the human body is not actually human at all. I wonder if lymphocytes are actually human cells, or symbionts. Or maybe only recently sucked into the human genome? Wait, not human. Vertebrate--lymphocytes are diagnostic of vertebrates, right? So maybe lymphocytes in primitive vertebrates might still be bacterial symbionts? Or is this all just nonsense?