BACKGROUND/AIM: Spontaneous regression (SR) of tumours is a rare phenomenon not yet fully understood. The aim of this study was to investigate immune cells infiltrating progressive and SR tumours in a Lewis rat sarcoma model. MATERIALS AND METHODS: Rats were subcutaneously inoculated with rat sarcoma R5-28 (clone C4) cells. Developing tumours were obtained on day 42 and cryosections were immunohistochemically processed for detection of immune cells. RESULTS: A high density of granulocytes was found in the necrotic areas of both progressive and SR tumours. CD4+ cells and CD8+ cells were rare and sparsely dispersed in the tumour tissue without clear difference between the two types of tumours. On the contrary, CD161+ cells were abundant and evenly distributed in SR tumours, but these cells were very rare in progressive tumours. CONCLUSION: Based on the differences in number and distribution of the immune cell subpopulations, we believe that natural killer (CD161+) cells play a major role in the destruction of cancer cells during SR of tumours in this Lewis rat model.

• Keywords
• CD161, CD4, CD8, Tumour, immunohistochemistry, spontaneous regression,
• MeSH
• Killer Cells, Natural pathology   MeSH
• CD4-Positive T-Lymphocytes pathology   MeSH
• CD8-Positive T-Lymphocytes pathology   MeSH
• Immunohistochemistry MeSH
• Rats MeSH
• NK Cell Lectin-Like Receptor Subfamily B genetics   MeSH
• Humans MeSH
• Disease Models, Animal MeSH
• Rats, Inbred Lew MeSH
• Gene Expression Regulation, Neoplastic MeSH
• Sarcoma genetics   pathology   MeSH
• Neoplasm Regression, Spontaneous genetics   pathology   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• NK Cell Lectin-Like Receptor Subfamily B MeSH