Morphological and morphometric studies of the splenic antitumor immune response, elicited by liposome-covered soluble p53 kDa antigen, in chemically-induced rat colon cancer

We evaluated the splenic morphometric changes in rats treated With carcinog en to study development of anticancer immune response. When liposome-covere d soluble 53 kDa antigen (s53) was injected into these rats, significant tu mor-suppression was seen and the percentage of turner-free animals rose fro m 15.4% in non-vaccinated rats to 53.8%. In the spleens of carcinogen treat ed rats that did not develop tumors, activity of B lymphocytes increased si gnificantly. This was manifested by the expansion of the germinal centers t o 50.9% of the follicular area reflecting depletion of B cells. and the dec rease of the mantle layer to 48.9% of the follicles. A similar picture was seen with T lymphocytes: the area of the marginal zone decreased to 55.2% o f the T zone of the white pulp, and that of the periarterial lymph sheaths (PALS) to 33.6%. In tumor-bearing rats features of the immune decompensatio n were seen: the germinal centers increased to 96.5% of the follicular area , and the mantle layer and PALS decreased significantly. Vaccination preven ted these effects, especially in tumor-bearing rats: the PALS occupies 30.4 % of the white pulp and the marginal zone 56.1%, and the mantle layer occup ied 58.1% of the follicular zone. Similar changes were found in vaccinated rats without tumors reflecting the compensatory character of the immune rea ction in vaccinated rats. In conclusion, we found that treatment with carci nogen followed by vaccination with the s53-liposomes complex stimulated the activity of the splenic B, and to a lesser degree the T systems.