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
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.
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.