In vivo studies of spleen lymphoid cells implicated in antitumor immunity in hamsters

Induction of simian virus 40 transplantation immunity in hamsters by gel-purified SV40 large T antigen

Simian virus 40 (SV40) large T antigen and p53 cellular protein were isolated from an SV40-transformed hamster cell line by immunoprecipitation with anti-T sera and purified by sodium dodecyl sulfate-gel electrophoresis. These two protein were tested in hamsters for the presence of SV40 transplantation rejection antigenic sites by in vivo transplantation rejection assay. The large T antigen immunized the hamsters against a challenge of SV40 tumor cells and the protected animals generated cytotoxic spleen cells. Hamsters immunized with the p53 cellular protein were not protected against SV40-induced tumor but there was some delay in the appearance of tumor.

Spleen cell populations in normal and tumor-bearing hamsters

Spleen cell subpopulations from normal and tumor-bearing hamsters (TBH) were quantified using Petri dishes coated with specific antibodies, and by flow cytometric immunofluorescence analysis. The relative numbers of T cells (Thy + cells) decreased, by both methods, as a function of tumor growth, while the number of B cells (bearing surface Ig) increased. Cells without T or B markers (null cells) were more numerous in the spleen of TBH and a large number of them expressed the receptor for the Fc fragment of IgG. Splenic cells were also sorted according to their light-scattering properties, and electron microscopic analysis was performed on the sorted fractions. It showed the presence of secreting plasmocytes and activated macrophages in the spleen of TBH.