For 10 points, name these proteins in the immune system that defend against antigens.
These molecules' variable regions use induced fit to bind to epitopes. Human types of them include E, involved in allergic reactions, and M, a pentamer produced in response to mismatched blood transfusions. Autoimmune diseases occur when they mistakenly attack self, rather than foreign, molecules. They are produced by B cells and are also known as immunoglobins. For 10 points, name these proteins in the immune system that defend against antigens.
These molecules' variable regions use induced fit to bind to epitopes.
{antibodies} [accept {immunoglobins} until mentioned]