Antigens

... and fungi (poly-N-acetylglucosamine), they are important for cell adhesion (in cell junctions), they are important in the immune system (a lot of antigens are actually sugar molecules) etc.

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... immune system has many components (located on the cell surface or secreted into plasma, for example), but in general they target such pathogenic antigens/structures that are common to microbes but not present in the host body. This way the receptors that recognize these can be assembled straight ...

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Vaccines generally present antigens - some molecule that sticks out of a pathogen - that the vaccinated can make antibodies to. To just use a protein from the pathogen will rarely work - even if it is a protruding protein, say a marker ...

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... many other types of macromolecules. They do not do this for nutritional purposes, though, but in order to break down the virus and display viral antigens to other immune cells so that they can identify and fight this type of virus. As a result, the remains of the virus are recycled by the body's ...

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... As for the second one you're on the right track. Why doesn't it seem right that that none are O. Remember that the blood groups refer to surface antigens of blood cells, A group just has A antigen, B just has B antigen, AB has both, and O has neither. If someone is O it means they have no alleles ...

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