CD80 and cancer: While Fc-mediated killing of medium-expressing HER2+ cancers is important for the anti-tumoral effect of tumor antigen-specific IgE in vivo, the mechanism of action of anti-HER2 IgE in vivo may include both Fc-mediated ADCC as well as priming of immune cells towards a pro-inflammatory state as we previously reported.15 20 Here we confirmed that cross-linking of anti-HER2 IgE antibodies on primary human monocytes resulted in phenotypic changes, including upregulation of CD40, CD80 and CD86 and downregulation of CD163.