HBB and COVID-19: In comparison, clusters D and E had proteins with higher levels in COVID-19 convalescents, e.g. immunoglobulins playing a role in antigen recognition (e.g. IGKV1-27, IGKV1-39, IGHV1-46, IGLV3-1, and PRDX2), hemoglobin subunits (e.g. HBB, HBA1, and HBD), and carbonic anhydrase (CA1).