Exploitation of phylogenetic distance in cell surface immune labeling: studies with beta 2-microglobulin.

Beta 2-microglobulin (beta 2M) is part of the HLA molecule, and is found on the cell surface of human nucleated cells. In certain skin tumors, malignant change has been associated with a loss of this surface beta 2M, indicating a possible diagnostic value for this marker. At present beta 2M is best identified in paraffin-embedded tissue by means of a triple-layer peroxidase-antiperoxidase technique, using mammalian polyclonal antisera. Recently a polyclonal antiserum against human beta 2M has been produced in chickens. Because of the phylogenetic differences between the species, the resulting antiserum is likely to recognize more epitopes on the beta 2M and show greater sensitivity than antisera raised in mammalian species. To confirm this hypothesis, the avian antiserum was compared to both mammalian polyclonal (rabbit) and monoclonal (mouse) antibody in vitro. beta 2M fixed to plastic surfaces combined with more avian than mammalian antibody. Furthermore, insolubilized chicken antibody could bind more secondary antibody-horseradish peroxidase conjugate than could insolubilized mammalian antibody, thus showing even greater enhancement with this system. Immunohistochemical analysis of these systems confirmed that the chicken strategy has greater sensitivity, and can be used in an indirect system with consequent reduction in nonspecific background activity. It is the most suitable technique for the investigation of the distribution of beta 2M in paraffin-embedded tissue.