A unique marker found on the surface of cells that have the potential to stimulate an immune response; antigens are basically the identity marker of cells for the immune system to see.
A group of normally inactive proteins in the blood that are activated by antibodies during an infection; complement proteins join together to form a membrane attack complex that pierces cell membranes, causing damage to the pathogens that are invading us.
A chemical secreted by mast cells and basophils that promotes inflammation by causing capillaries to become more permeable.
Also known as non-specific immunity, innate immunity consists of general physiologic responses (fever, inflammation, etc.) that can affect the entire body.