Immunohistochemical study of the inflammatory infiltrate associated with equine squamous cell carcinoma.

The research investigates the inflammatory response related to squamous cell carcinoma in horses. The study examines different immune cell types in and around the cancerous and pre-cancerous tissue, and their relevance to the disease’s progression or containment.

Research Design and Subjects

• Various immune cells and related proteins were investigated within an inflammatory response related to 19 cases of equine squamous cell carcinoma (SCCs). These included T lymphocytes (CD3), B lymphocytes (CD79), plasma cells producing immunoglobulins (IgG, IgM, IgA), macrophages, and MHC Class II antigen.
• Some pre-cancerous cases (actinic keratosis) were also included in the study to compare with the cancerous cases.
• The squamous cell carcinomas came from different body parts of the horses – including the penis, conjunctiva, skin, nasal cavity, and oral cavity.

Finding Protection among the Infection

• They found an abundant inflammatory response associated with most of the SCCs and pre-cancerous lesions. This response was composed mainly of T lymphocytes, B lymphocytes, and a high number of plasma cells producing IgG.
• By contrast, plasma cells producing IgM and IgA were hardly noticed, appearing in limited and variable quantities.
• Macrophages were often numerous in number. Additionally, these macrophages, along with lymphocytes, intra-epithelial dendritic cells, and fibroblasts were found to express the MHC Class II antigen.

Correlation with Disease Progression

• Importantly, the researchers found no substantial correlation between the type or degree of inflammatory infiltrate and the SCC’s histological grade or degree of invasion. This lack of relationship suggests that the local anti-tumor immune response could not prevent tumor invasion or metastasis.
• On the other hand, MHC Class II was found to be expressed by varying numbers of neoplastic cells in four of the SCCs. These four cancers were only locally invasive, not spreading to distant sites.
• Detailed observations around areas where SCC cells expressed Class II antigen revealed numerous T lymphocytes, some associated with degenerate tumor cells. This discovery suggests that the expression of MHC Class II by cancerous cells might help improve the local immune response against the tumor.