The Role of MCA in Dermatology: Monoclonal Antibodies in Cutaneous Immunohistochemistry

Since the first demonstration of antibodies in sera of pemphigus patients by immunofluorescence in 1964, dermatology has become one of the leading clinical specialities applying immunohistochemical methods for both research and current diagnosis. The first step has been the study of Ig deposits in autoimmune or other immunologically related skin diseases such as, for example, pemphigus, pemphigoid, D.H. and L.E. In fact, the diagnosis of autoimmune diseases is no longer the only field of immunohistochemistry. More recently, IHC has been applied to a new field, the study of skin components, cell surface antigens, molecules, and fibers such as collagen, keratin, and cellular cyto‐skeleton (1). The indicators for studying skin antigens are the corresponding antibodies. Autoantibodies reactive with the epidermis have facilitated the study of skin structures in normal as well as in diseased skin. Nevertheless, the field of such studies remained limited because few antisera were available. In a large majority of cases, antigens were unknown and nonbiochemically studied. Therefore, attempts have been made to produce heterologous conventional antisera against various components of the skin. For example, in 1980 (2) J. Viac in our group produced antikeratin antisera by immunizing guinea pig and rabbits with either whole keratin or polypeptidic bands isolated on polyacrylamid gels. Such antibodies recognized different antigenic species of keratins and provided a good method for studying normal epithelia and tumors. Conventional polyclonal antisera, however, have some disadvantages. They may lack specificity and vary a great deal, even though the same immunogens are used for their production. In fact, many polyclonal antisera are available and may be used for keratin and other filaments such as actin, vimentin, and myosin and for fibrous proteins such as laminin, fibronectin, collagens, and amyloid. Until recently, there has been only slow progress in the methods for producing specific antibodies. In 1975, Köhler and Milstein described a fundamentally new approach: the production of antibodies by somatic cell hybridization of antibody‐forming cells and continuously replicating cell lines. This technique has allowed preparation of virtually unlimited quantities of antibodies that are chemically, physically, and immunologically completely homogeneous (3–5). MCA have become some of the most widely utilized tools for immunological research. An explosion of MCA makes them available for use in cutaneous immunopathology and the field of application is enlarging very quickly. In this article, some aspects of the production methods of utilization and examples of applications of MCA in cutaneous immunohistochemistry will be discussed.