Monoclonal antibodies are identical antibodies that are produced by one type of immune cell and are directed against a specific epitope or antigen. They are typically created by fusing myeloma cells with spleen cells from a mouse that has been immunized with the desired antigen. This fusion forms a hybridoma cell line that can produce monoclonal antibodies. Monoclonal antibodies have important diagnostic uses in detecting conditions like pregnancy and infections. They are also used therapeutically for cancer treatment.