The role of immune cells in tumor growth and spontaneous regression in a rat sarcoma model

The aim of the thesis is to study differences between sexes of rats in tumour growth, the difference in immune response between rats with progressing and spontaneously regressing tumours compared to control rats and verification of immunological memory. We used Lewis rat model with subcutaneously inoculated sarcoma. Peripheral blood of males showed a higher number of red blood cells, a higher concentration of haemoglobin and higher haematocrit compared to females. Experimental females with inoculated sarcoma had higher levels of CD161 (NK) cells at the beginning of experiment in comparison with the experimental and control males and control females. A strong infiltration of NK cells was observed in tissue sections of spontaneously regressing sarcoma compared to progressing tumours tissue. Important factors that can influence if the animal will show tumour progression or spontaneous regression are neutrophil granulocytes (they can induce both tumour-supporting and anti-tumour response), vascularization and extent of necrosis in tumour tissue. We have verified immunological memory in a small group of females by the secondary inoculations of the same tumour cells after complete disappearance of primary, spontaneously regressing tumour. No sarcoma repeatedly evolved in any of the females. Results obtained in the present work brought new insights into the problems of tumour in the Lewis rat sarcoma model with inoculated sarcoma. These results may have significance also for area of clinical oncology due to similarities with the behaviour of some human cancers