Immunological classification of a pike lymphoma

Area of Science:

• Comparative pathology
• Immunohistochemistry
• Fish oncology

Background:

• Intermediate filaments (IFs) are crucial cytoskeletal proteins with conserved structures across species.
• Understanding IF expression aids in classifying tumors, particularly in non-mammalian vertebrates like fish.
• Northern pike (Esox lucius L.) are susceptible to various neoplasms, necessitating accurate diagnostic methods.

Purpose of the Study:

• To characterize the intermediate filament (IF) protein expression in northern pike (Esox lucius L.) tumors.
• To determine the cellular origin of the pike neoplasm (mesenchymal vs. epithelial, muscle, neural, or glial).
• To assess the immunological characteristics of tumor cells compared to normal hemic cells.

Main Methods:

• Indirect immunofluorescence microscopy using monoclonal and polyclonal antibodies against mammalian IF proteins.
• Analysis of frozen tissue sections from northern pike tumors and healthy tissues.
• Immunoglobulin expression and rosette formation assays on peripheral blood, spleen, head kidney, and tumor cells.
• Lymphocyte proliferation assays using various mitogens on mononuclear cells.

Main Results:

• IF analysis confirmed tumor cells expressed vimentin but lacked cytokeratin, desmin, neurofilament proteins, and glial fibrillary acidic protein, indicating a mesenchymal origin.
• Tumor cells showed significantly lower immunoglobulin expression and rosette formation compared to normal hemic cells.
• Mononuclear cells from normal pike tissues responded robustly to T and B cell mitogens, while tumor cells exhibited a lack of proliferative response.

Conclusions:

• The neoplasm in northern pike is a mesenchymal tumor, likely of hemic cell origin.
• The tumor cells display characteristics distinct from normal immune cells, suggesting immune evasion or dysfunction.
• This study provides valuable insights into fish tumor classification and immune cell behavior in neoplasms.