Monoclonal antibodies: diagnostic tools

Monoclonal Antibodies Diagnostic Tools and Therapeutic Agents... 

Each additional immunization and each individual animal creates a different pattern of specific antibodies. This peculiar situation may limit the continuity of long-term studies using only polyclonal antibodies as diagnostic tools. On the other hand, polyclonal antibodies are almost not susceptible to single mutations of antigens, and therefore they are more proper in all cases when a more broadly specificity is desired. In practice the question is not if monoclonal antibodies are better than polyclonal antibodies. Requirements and problems in diagnosis of livestock diseases are individually different and it will be advantageous and helpful if both types of antibodies are available and combinatorial use is possible. 

The immunoglobulin fraction derived from the polyclonal hyperimmune serum of humans and animals has been used clinically in combating conditions such as bacterial infections and maternal immunization by Rh-positive cells from the fetus. Polyclonal sera raised against proteins have also been valuable diagnostic and research tools. However, the undefined composition of polyclonal antisera results in wide and unpredictable cross-reactivities. Furthermore, the quantities of antibody available are limited to the amount of serum an immunized animal can yield. Monoclonal antibodies described below circumvent these problems of definition and quantity associated with polyclonal sera. 

Compared with the therapeutic use of human monoclonal antibodies, the use of rodent (mouse or rat) monoclonal antibodies in vivo is disadvantageous because the xenogeneic antibody can induce immune responses that will mitigate the effectiveness of the antibody and/or cause adverse reactions in the recipient. Thus, the authors of one report concluded that antimouse immunoglobulin responses in human patients have limited the usefulness of murine monoclonal antibodies in more than half of those treated (12). The formation of human antimouse antibodies has been described both when murine monoclonal antibodies are used as a diagnostic tool in vivo and when they are used therapeutically (13-16). 

FIGURE 1.8 (A) Direct biotin-avidin method. The primary antibody is linked to biotin (B) an avidin-peroxidase-conjugate (A-Px) is then added. (B) Indirect biotin-avidin method. Used for monoclonal antibodies, the primary antibody is not conjugated its localization is detected by a biotinylated secondary antibody. Boxed asterisk represents antigen determinant on primary antibody. Px, peroxidase label A, avidin B, biotin. From Taylor CR, Cote RJ, eds. Immunomicroscopy A Diagnostic Tool for the Surgical Pathologist. 3rd ed. Philadelphia Elsevier 2005 21. 

FIGURE 1.19 (A, B) B5-fixed section of bone marrow aspirate depicting a small solitary nodule consisting of lymphocytes and occasional plas-macytoid lymphocytes, with scattered plasma cells around it. Many of the lymphoid and plasmacytoid cells reacted strongly with anti-lambda antibody (A). Anti-kappa reacted only with scattered plasma cells outside the nodule (B, small black dots). This patient eventually was shown to have a solitary plasmacytoid lymphocytic lymphoma in the small intestine (also lambda type). Paraffin sections, DAB with hematoxylin counterstain (xl 25). There was no serum paraprotein detectable at this time presumably the number of tumor cells was insufficient for production of a detectable paraprotein however, a "monoclonal" IgM appeared later in the course. From Taylor CR, Cote Rj. Immunomicroscopy A Diagnostic Tool for the Surgical Pathologist 2nd ed. Philadelphia WB Saunders 1994 59. 

The type 1 TLS/CHOP chimeric transcript is a result of the above-mentioned t(12 16) and is a very sensitive and specific molecular alteration for the myxoid/round cell liposarcoma entityOikawa and colleagues have developed a monoclonal antibody to this fusion transcript, which they claim is highly specific and sensitive with formalin-fixed paraffin-embedded tissue. However, there is no literature on its use. As a diagnostic tool, this is a good example of a genomic application of me. 

---