CD79A and neoplasm: In support of the notion that IgA indeed transcytoses through tumour cells, several peptides of the secretory component were detected in the supernatants of OVCAR3, OVCAR4, OVCAR5 or primary ovarian cancer cells incubated with IgA, but not when these cells were co-incubated with the transcytosis inhibitors wortmannin and brefeldin A9,10, or when cells were incubated with IgG (Fig. 2b, Extended Data Fig. 4b–e, Supplementary Data 1, 2).