IGHA1 and nasopharyngeal carcinoma: Higher somatic hypermutation (SHM) frequencies of IGHA1, IGHG1, and IGHG3, reflecting higher affinity of BCRs associated with antigen recognition and activation29,30, were observed in B cells derived from NPC tissues compared with that from PBMC, as were higher clonality and proportion of IGHA1 and IGHG1 isotypes (Supplementary Fig. 6a).