I refer you all to a paper published in 2016 in Current Allergy and Asthma Reports entitled: “IgG4 Characteristics and Functions in Cancer Immunity”.
This paper reveals that not only is there a link between tumor progression and the presence of IgG4 due to class switching, but that this link might even be necessary for tumor promotion and progression.
Let’s really do some background on IgG4. It’s different from its brother and sister IgG subclasses for a very interesting reason: it can swap out its arms – even it’s entire half – if it so feels like! This is called Fab arm exchange. It’s Fab! Well, not in the context of cancer.
… Now that you understand perfectly how important these antibody functions are for removing unwanted cells and foreign material, you can imagine how important they might be in suppressing tumor formation by suppressing the growth rate of cancer cells. Be very aware, these mechanisms of action are enacted by the IgG1 subclass. So the question becomes, what happens in the context of cancer, specifically, when the antibody subclass ratio changes due to chronic exposure to antigen? Or more precisely, what happens when the IgG1: IgG4 subclass antibody ratio inverts in the context of tumor suppression?