Host Interferon gamma Production and STAT-1 Signalling Is Crucial for Minor Antigen Mediated Rejection of High Grade Lymphoma.

Abstract

To date mechanisms of T-cell mediated immunity and immune-escape in high grade lymphomas are poorly understood. Using a transgenic mouse lymphoma model, where the proto-oncogene c-myc is driven in parts of the immunoglobulin lambda locus representing a t(8;22) translocation as found in Burkitt's lymphoma, we developed a syngeneic model to investigate the anti-lymphoma activity of lymphoma specific T-cells. By retroviral transduction of a lymphoma specific antigen (chicken ovalbumin-IRES-GFP vector) into primary cell lines from c-myc transgenic lymphomas we established a model that would allow us to investigate the contribution of interferon gamma signalling in rejection of high grade lymphoma. All lymphomas established displayed low MHC class I and II levels on the surface when compared to wildtype B-cells. This expression could be enhanced by treatment with interferon gamma (100U/ml) up to 10 fold. When retrovirally transduced lymphoma cells were injected into wildtype or GFP transgenic C57BL/6 recipients, animals displayed a significant delay in lymphoma growth compared to IRES-GFP transduced control cell lines. 50% of the recipient mice rejected OVA containing lymphomas whereas we observed a 100% lymphoma growth of IRES-GFP transduced lymphomas in GFP transgenic recipients. Developing OVA containing lymphomas displayed a loss of GFP expression indicating a selection for non transduced cells. In spleens from mice successfully rejecting OVA-containing lymphomas we found up to 1.5% (±0.12%) SIINFEKL specific T-cells. To gain mechanistic insights of lymphoma rejection, we transferred OVA transduced lymphoma cells to Stat1−/− and IFNg−/− recipients. Lack of STAT1−/− on the recipient side or inability to secrete interferon gamma was associated with fast lymphoma progression and was not different when compared to IRES-GFP transduced cell lines injected into GFP transgenic hosts. Although we found 1.6% (±0.52%) SIINFEKL T cells in spleens of lymphoma bearing STAT1−/− animals, interferon gamma production was significantly decreased. We could also show that in wild type recipients, OVA containing lymphomas displayed high MHC class I and II expression which is completely absent in lymphomas from Stat1−/− recipients. Our results suggest that rejection of high grade lymphoma by a specific minor antigen is possible and Stat1 signaling and interferon gamma production by the host is crucial for lymphoma rejection.