How is a macrophage adapted to perform its function?

1) Yes you're quite right. It is very flexible. It undergoes a process whereby it squeezes out. This happens because it is attracted to chemicals released by other immune cells that have found the invasion. These chemicals cause the wall of nearby blood vessels to stick out special markers that the cell adheres to, a bit like velcro. It has one part and the cell is the other. This causes the cells to slow down and roll along the blood vessels until it stops. This is when it then squeezes through. Inflammation from the nearby trauma or invaders cause blood vessels to become leaky and have gaps in them (which is one reason you get swelling as fluid and leak out). This helps the macrophages escape.

2) They recognise various molecules on the cell surface. DAMPS (damage associated molecular patterns) are things that only appear if the tissue is damaged. Like if you broke a mars bar in half, you'd see the caramel etc, but you don't normally see that. PAMPS are Pathogen associated molecular patterns. These are patterns of molecules, often cell surface receptors (suckers on the outside of the cell tha do various things), that are only ever seen on pathogens.

There are other ways too. If a cell is infected virally, it can put a little flag on its surface that says "I am infected" and release molecules called "interleukins" that go to adjacent cells and warn them of an incoming threat.

3) The macrophages look for cells that show something weird, or don't show what they're expecting. They then move to suck it in, and dissolve it using free radicals or acidic substances in things called "phagolysosomes". The "phagosome" is the bubble inside the macrophage that contains the foreign particles or bacteria, and the lysosome is what contains the toxic chemicals. These fuse and become "phagolysosomes".

Macrophages can then show bits of debris from the phagolysosome on its cell surface and present this to the rest of the immune system, saying "look what I found! Its gross! Amass an army against it!". It has a marker on it that tells the body it is a helpful macrophage (like an ID card) and so the body is happy for it to present a piece of the invader.


Does that start to help?

Happy to chat more if it isnt helpful!