To define the relative contribution of antigen recognition by tumour-derived IgA to delayed malignant progression, we produced recombinant dimeric IgA antibodies by cloning the matching VH and VL sequences of three clonally expanded, IgA-producing tumour-derived B cells, as determined by single-cell B cell receptor sequencing (Supplementary Data 5). The gene discussed is CD79A; the disease is neoplasm.