Cutaneous tumor of northern pike, Esox lucius L. II. Expression of surface and cytoplasmic immunoglobulins and alpha-naphthyl acetate esterase by mononuclear cells from lymphoid tissues and tumor.

Rabbit anti-pike IgM antibodies showed that up to 95% of mononuclear (MN) cells isolated on Ficoll-Isopaque gradients from peripheral blood, spleen, and head kidney of northern pikes carrying cutaneous tumors were surface (SIg) and cytoplasmic (CIg) immunoglobulin positive by indirect immunofluorescence. On the contrary, rabbit anti-winter flounder IgM antibodies gave totally negative results. Monoclonal anti-carp IgM antibodies stained approximately 40-56% of peripheral blood, splenic, and head kidney MN cells in assays for SIg and CIg. Monoclonal anti-rainbow trout IgM antibodies, however, did not cross-react with pike Ig. A maximum of 5% of MN cells from the tumor were SIg and CIg positive by anti-pike IgM as well as 6% by anti-carp IgM antibodies, and were negative by the other two antibodies even at low dilutions. A majority of cells in the tumor exhibited an intense diffuse staining pattern for alpha-naphthyl acetate esterase (ANAE) which was inhibited by sodium fluoride and was reminiscent of that noted in human monocytes. These findings show that the Aland pike neoplasm is not a B cell tumor or plasmacytoma, but more representative markers are needed to demonstrate whether it is of T lymphocytic or monocytic origin.