Antibody Production

In an animal’s primary immune response, the first antibodies made are the IgM class. IgM molecules form large pentameric polymers in the serum. When the animal’s immune system is challenged with the same antigen again, a secondary immune response occurs. The secondary immune response is largely made up of IgG molecules. IgG molecules are the most common circulating antibodies in the immune system, and these are the most common type of antibody used in cell biology. Because of the nature of an immune response, the immunoglobulins specific to a particular antigenic determinant are only part of a large pool of antibodies. Each immunoglobulin produced from each B cell is the result of a proliferated response from that antigen stimulation, and the serum contains the whole mix of clones from many B cells, and is called polyclonal antiserum.

It is possible to have antibodies generated from one single B cell that results in a homogenous population of antibody, or monoclonal antibody. Monoclonal antibodies can be produced by a hybridoma technique which is the fusion of the B cell with a myeloma tumor cell to form a hybrid cell. In practice, after a mouse has been immunized and has an active immune response, the spleen tissue is removed so that the B cells can be isolated and fused with myeloma cells. The tumor cell lends the ability to grow in culture to the antibody-producing B cell, so that in culture, clones of the hybridoma cells survive and single clones are selected to produce a supply the monoclonal antibody. The antibody can be grown in culture or can also be perpetuated by injecting the hybridoma back into a mouse where monoclonal antibodies are removed in the ascites fluid.