A while ago, I wrote about how Helicobacter pylori, the bacteria that cause stomach ulcers and are implicated in certain stomach cancers, cause the cells of the stomach wall to die. H. pylori kills cells very sneakily, by releasing a chemical that causes them to commit suicide. It turns out that this is not the only sneaky trick H. pylori has, it can also hide from the immune system by changing its outer cell membrane.
The immune system protects your body from any invading elements, and because of this it needs a way to distinguish body cells from invading cells. The cells of the immune system do this by recognising bits of bacteria as foreign invaders, and of course the first bit of the bacteria they see is the outer cell membrane. H. pylori has a way of making parts of its outer cell membrane look very similar to human blood group antigens, so the immune cell doesn’t recognise it as an invader.
Click "source" for entire article.