Immunisation of an animal with an antigen results in the production of polyclonal antibodies in other words, different antibodies with different specificities and affinities. A monoclonal antibody refers to an antibody obtained from a population of substantially homogeneous antibodies. They are highly specific, being directed against a single antigenic site. While polyclonal antibodies are advantageous for the immune system, the production of monoclonal antibody, which is derived from a single plasma cell and is specific for one epitope is more useful for the growing market of in vitro and in vivo diagnostic products and therapeutics. 

Uses of Monoclonal Antibodies

Purification of proteins. For example, one can take a complex mixture of proteins, immunize mice and then produce monoclonal antibody to the protein of interest. One can then attach this monoclonal antibody to beads to form an immunoadsorbent column which can be used to purify the protein of interest.

Identification and isolation of various lymphocyte subpopulations. For example, monoclonal antibodies to CD4 and CD8 can be labeled with two different fluorochromes and incubated with a lymphoctye preparation. The TH and Tc cells can then be separated in a fluorescence activated cell sorter.

Tumor detection and elimination. Monoclonal antibodies specific for certain tumor associated membrane proteins can be produced. Tumor specific monoclonal antibody can also be conjugated to a lethal toxin to form what is sometimes called an immunotxin that is capable of killing tumor cells. Such immunotoxins can be directed against cell membrane antigens of various cancers.

Diagnostic reagents for things like bacterial and viral pathogens. Many of these test kits use strips of paper impregnated with an appropriate monoclonal antibody.

Virus Detection and eliminination: Monoclonal and polyclonal antibodies have been shown to react with surface components of cells infected by HIV primary isolates, indicating that targeted cells express surface antigens which can induce and bind antibodies. Neutralizing anti-HSN1 human monoclonal antibodies have been generated from the peripheral blood of patients who had recovered from infections with HPAI H5N1 viruses (Simmons, “Prophylactice and therapeutic efficacy of human monoclonal antibodies against H5N1 influenza” PLoS Medicine, 4(5), 2007, 3178).