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 sections of three cats using immunohistochemistry. Reactivity of the antibodies was tested on feline tonsil, intestine, thymus, lymph node and spleen with a three-step immunoperoxidase technique and compared with reactions on human thymus, lymph node and spleen. From a total of 95 antibodies, 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 molecules (VLA-2 and VLA-4), to natural killer (NK) cells (CD56, CD57 and NCAM), to complement receptor CR1, to proliferation marker Ki-67 (MIB-1), to endothelial antigens (EN-4, PAL-E and von Willebrand factor) and to structural proteins like vimentin, desmin, collagen type IV and cytokeratin. 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 system.