Immunology

Monoclonal Antibodies

Monoclonal antibodies are made by identical immune cells that are all clones of a unique parent cell. Monoclonal antibodies can have monovalent affinity, in that they bind to the same epitope. However, bispecific monoclonal antibodies can also be engineered, by increasing the therapeutic targets of one single monoclonal antibody to two epitopes.

Fig: Monoclonal and Polyclonal Antibodies

A technique to produce monoclonal antibodies was devised by Georges Kohler and Cesar Milstein in1975. Monoclonal antibodies are single antibodies made by fusing antibody-producing cells with an immortalized cell line, resulting in a cell line called a hybridoma. Hybridomas are separated by the individual antibodies that the different cells make, until you have a “pure” cell line that produces a single antibody.

The method relies on fusing B cells from an immunized animal (typically a mouse) with an immortal myeloma cell line and growing the cells under conditions in which the unfused normal and tumor cells cannot survive. The resultant fused cells that grow out are called hybridomas; each hybridoma makes only one Immunoglobulin, derived from one B cell from the immunized animal. The antibodies secreted by many hybridoma clones are screened for binding to the antigen of interest, and this single clone with the desired specificity is selected and expanded. The products of these individual clones are monoclonal antibodies, each specific for a single epitope on the antigen used to immunize the animal and to identify the immortalized antibody-secreting clones.

Monoclonal antibodies target various proteins that influence cell activity such as receptors or other proteins present on the surface of normal and cancer cells. The specificity of monoclonal antibodies allows it’s binding to cancerous cells by coupling a cytotoxic agent such as a strong radioactive which then seek outs to destroy the cancer cells while not harming the healthy ones.

                                                  Fig: Binding of Monoclonal Antibodies

The presence of a large amount of a specific monoclonal antibody in the blood means that there is an abnormal protein. Typically this protein can be detected during a physical examination and is identified using a screening blood test called “protein electrophoresis. The source of abnormal production of monoclonal antibody is a small population of plasma cells in the bone marrow.

 

Monoclonal Antibodies are far more effective than conventional drugs since drugs attack the foreign substance & the body’s own cells which cause harsh side effects while, the monoclonal antibody only targets the foreign antigen/target molecule, without or only minor side effects.

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