ISOLATION AND CHARACTERIZATION OF THE CANINE MELANOMA ANTIGEN RECOGNIZED BY THE MURINE MONOCLONAL-ANTIBODY IBF9 AND ITS DISTRIBUTION IN CULTURED CANINE MELANOMA CELL-LINES

Objective-To characterize the canine melanoma antigen recognized by th e murine monoclonal antibody IBF9 as to its cellular location, molecul ar size, protein and glycogen contents, and distribution in cell lines . Sample Population-7 cultured canine melanoma cell lines. Procedure-M olecular characteristics of the antigen were determined by western blo tting, enzymatic digestion studies, and tunicamycin inhibition studies . Distribution of the antigen in the cultured melanoma cell lines was determined by flow cytometry. Results-The antigen consists of 2 protei ns with molecular mass of 89 and 85 kd. Tunicamycin and enzymatic dige stion studies indicated that these proteins contained little glycosyla tion. Immunogold and immunofluorescence studies localized the antigen to the cell surface; Antigen expression was consistent within each cel l line, with > 90% of the cells positive for all cell fines except 1 ( 80%). Percentage of positive cells and relative intensity of immunosta ining were constant throughout ail phases of the cell cycle. Conclusio ns-The antigen identified by MAB IBF9 is a well-conserved and highly e xpressed cell surface protein present during all phases of the cell cy cle in all malignant canine melanoma cell lines examined. Clinical Rel evance-Because of consistency in expression, the antigen may have pote ntial for use in dogs for melanoma immunodiagnostics and immunotherapy .