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Small Animal Section: No. 19DIAGNOSTIC IMMUNOHISTOCHEMISTRY:1. TUMOUR MARKERSCell markers are available for identification of cell origin, and are used for determining tumour cell lineage. This additional test is especially helpful in the determination of the origin of neoplastic cells, which appear anaplastic or undifferentiated with routine histopathological examination. Tumour markers play an important prognostic role in tumours where the cell type influence the biological behaviour of the neoplasm. The following cell markers are available for veterinary use in South Africa:
These immunohistochemical cell markers must always be used in conjunction with histopathological examination. In some neoplasms a battery of these cell markers may be necessary to arrive at a specific cell lineage of origin for the neoplastic cells
In cases of suspected autoimmune disease immunoglobulins or complement within the skin are detected using the immunoperoxidase staining method. IHC can be used to determine the type of autoimmune disease present, as different patterns of IgG deposition is noted, in the different diseases:
- Intercellular epidermal staining: Pemphigus group of disease - Linear band at the basement membrane zone: DLE, SLE, pemphigus erythematosus, bullous pemphigoid - Blood vessel wall: immune-mediated vasculitis, some cases of SLE.
A diagnosis of immune-mediated skin disease must be based on a combination of appropriate clinical signs, compatible histological lesions, positive IHC test and response to immunosuppressive therapy.
Pitfalls: - False positive staining may be detected in normal footpads and nasal planum or in inflammatory diseases (e.g. Staph. folliculitis, demodicoses, sarcoptic mange, dermatomycosis), where Ig and complement may be deposited secondary to tissue damage. - False negatives may occur due to corticosteroid therapy in the preceding 3 weeks, or failure to sample a primary lesion - Sampling of ulcerative lesions may only reveal secondary changes and inflammation. Primary (early) lesions e.g. vesicles must preferably be submitted.
3. INFECTIOUS DISEASES Immunohistochemistry involves the detection of antigen within formalin-fixed tissue sections with the use of antibodies and visual marker substances. The immunoperoxidase staining technique can be used to determine the presence of certain infectious agents/antigens within histological sections. Commercially available antibodies are used to bind to the specific antigen in the tissues, and thus cause a positive staining reaction. The following infectious diseases can be detected with IHC in South Africa:
The advantage of Diagnostic Immunohistochemistry, is that formalin-fixed tissues are used, and routine histological samples are thus adequate. For further information contact:
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For any animal pathology queries, please send e-mail to
info@vetpath.co.za. |
