How do white blood macrophages eat? Does it affect their ability to protect us?

(written by lawrence krubner, however indented passages are often quotes). You can contact lawrence at:, or follow me on Twitter.

A few questions just occurred to me, which I will try to research some time soon:

When white blood cells (macrophages) are drifting around in our blood, how do they eat? It would seem they could eat whenever they want, since our blood is full of food. But are macrophages as effective while eating? Are we vulnerable when they eat? Fasting seems to improve health, so we should assume macrophages are less effective when we eat? And alcohol seems to depress the effectiveness of our immune system.

We should never show weakness to our enemies. And millions of years of evolution would surely teach this, both to our macrophages and to the pathogens that tend to attack mammals. So when our macrophages are injured, they probably try to hide that fact? And meanwhile, pathogens are probably eager to get that information? Are there any chemical signals that are unique to sick macrophages? That might help explain why people’s lives tend to end in a cascade of problems — once pathogens sense weak macrophages, they might suddenly all attack at once.