For purposes of research and use in medicine, antibodies are often isolated by sacrificing animals after hyper immunizing them with antigens. From such hyper immunized animals, the blood serum may be taken and antibodies may be isolated from this serum. However, the antibodies, whenever separated from serum after induction due to an antigen, are usually heterogeneous, because the cells keep on producing a variety of antibodies

Consequently, the antibody preparation made from serum will not have the desired specificity and, therefore, can not be utilized for diagnosis of screening. Monoclonal antibodies (Mabs), on the other hand, are homogeneous immunological reagents of defined specificity, so that these can be utilized for diagnosis and screening with ease and certainty.