Describe how a B-cell responds the first time it is stimulated by an antigen. [3 marks]

A B-cell with a specific antigen receptor will bind to a complementary antigen, when exposed to that antigen in the body. This specific complementary binding leads to that B-cell becoming activated. An activated B-cell then undergoes clonal expansion to produce multiple copies of itself. These multiple copies then differentiate into either plasma cells or memory cells. Plasma cells produce and secrete specific antibodies complementary to the original antigen that activated the B-cell. Memory cells have antigen receptors complementary to the specific antigen that activated the original B-cell and can stay in the body for >20 years, they allow for a quicker secondary immune response if exposed to the same antigen a second time. Keywords: - Clonal expansion - Specificity - Antibody - Plasma cells - Memory cells