Notably, multiple immunoglobulin chains (e.g., IGHG1, IGKV4-1, IGHG3, IGHV1-46, IGHA1, IGHG2, IGLC2, IGKV2-29, and IGKC) exhibited substantially lower expression in COVID-19-A patients; they showed slightly higher expression in COVID-19-R patients. Here, IGLC2 is linked to COVID-19.