IMMUNOHISTOCHEMICAL DEMONSTRATION OF CELLULAR ANTIGENS OF THE CAT DEFINED BY ANTI-HUMAN ANTIBODIES

A panel of monoclonal antibodies (mAb) and some polyclonal rabbit sera directed against human antigens were studied on cryostat tissue secti ons of three cats using immunohistochemistry. Reactivity of the antibo dies was tested on feline tonsil, intestine, thymus, lymph node and sp leen with a three-step immunoperoxidase technique and compared with re actions on human thymus, lymph node and spleen. From a total of 95 ant ibodies, 28 gave reactivity comparable with that in human tissues. The remaining antibodies gave none or miscellaneous results. The positive reactions in the cat included antibodies directed to adhesion molecul es (VLA-2 and VLA-L), to natural killer (NK) cells (CD56, CD57 and NCA M), to complement receptor CR1, to proliferation marker Ki-67 (MIB-1), to endothelial antigens (EN-4, PAL-E and von Willebrand factor) and t o structural proteins like vimentin, desmin, collagen type IV and cyto keratin. The identification of these cross-reacting antibodies extends the spectrum of immunological reagents that are now available for the cat, and will thus contribute to the study of the feline immune syste m.