ABSTRACT
Immunoglobulins (Ig) are polypeptides that function as antibodies in the immune response. They are produced by plasma cells, a type of mature B lymphocyte. Plasma cells are of lymphoid lineage and are produced by and mature in the bone marrow. They comprise about 30% of circulating lymphocytes. As a rule, plasma cells require both antigen and T lymphocytes for activation but some antigens, such as bacterial lipopolysaccharide, are capable of activating them directly.
