Tumour bound immunoglobulins. The fate of immunoglobulin disappearing from the surface of coated tumour cells

This paper confirms results showing that TA3 tumor cells coated in vivo with immunoglobulins, lose some of the coat upon transfer to in vitro conditions. By labelling IgG isolated from the ascitic fluid of TA3 tumors it was found that the immunoglobulin coating TA3 cells is dynamically exchanged with immunoglobulin in the corresponding ascitic fluid. Some of the released immunoglobulin is in a degraded state, judging from the fact that most of the released material loses the antigenicity of intact immunoglobulin and has a lower capacity to precipitate with ammonium sulphate at 50% saturation. The degraded immunoglobulin has a higher binding efficiency to tumor cells. In vivo experiments demonstrated that the ascitic fluid of mice bearing TA3 and MC1 M tumors contains a material which has some of the physicochemical properties of IgG but which does not precipitate with antisera directed against IgG.