Question

Differentiate between Antigen and antibodies.

Answer 1

Aspect	Antigen	Antibody
Definition	A substance that, when introduced into a vertebrate host, provokes an immune response leading to acquired immunity. It stimulates the formation of specific antibodies.	Specific proteins synthesized by the host in response to an antigen. They are immunoglobulins released from plasma cells.
Nature	Usually organic compounds of high molecular weight, mostly proteins (complete antigens). Some smaller molecules (haptens) are incomplete antigens that need to combine with proteins to stimulate antibody formation.	Proteins (immunoglobulins, Ig) made of monomeric units with two light and two heavy chains, linked by disulfide bonds. Five types exist: IgG, IgM, IgA, IgD, IgE.
Function	Acts as a target that triggers the immune response. Includes microbes, pollen, tumour cells, and foreign blood cells.	Bind specifically to antigens to neutralize them, form complexes, or facilitate their destruction by immune cells. Part of the humoral immune response.
Antigenicity	The property of an antigen to stimulate antibody formation.	Produced as a result of antigenicity; antibodies specifically recognize and bind to antigens.