We are working with the B16-OVA MO4 cell line (Millipore) to study the protective effect of immunogenic forms of OVA combined with anti-CD40 antibodies as adjuvants. Treated animals display a clear and robust T cell response, as determined by IFN-γ production in ELISPOT assays following stimulation with the SIINFEKL peptide. However, the level of tumor protection is minimal and comparable to that observed with the parental B16 line, which does not express OVA.

We are concerned that B16-OVA MO4 cells, whether or not they are pre-incubated with IFN-γ, do not show detectable levels of MHC I–SIINFEKL complexes, as assessed by flow cytometry using the 25-D1.16 antibody specific for H-2Kb–SIINFEKL. In contrast, the complexes are detectable (even more if pretreated with IFN-γ) when cells are exogenously pulsed with SIINFEKL peptide.

Additionally, significant levels of OVA are detectable in the culture supernatant of B16-OVA MO4 cells, but not in that of the parental B16 line. We would greatly appreciate any comments from others who have worked with this cell line and may have observed similar findings, particularly, with regard to their expression of MHC I–SIINFEKL complexes. Thanks