Corrigendum: Genetic Removal of the CH1 Exon Enables the Production of Heavy Chain-Only IgG in Mice - Zhang, Tianyi; Cheng, Xueqian; Yu, Di; Lin, Fuyu; Hou, Ning; Cheng, Xuan; Hao, Shanshan; Wei, Jingjing; Ma, Li; Fu, Yanbin; Ma, Yonghe; Ren, Liming; et al. (Frontiers in Immunology, 2019)