Anti-endotoxin human monoclonal antibody A6H4C5 (HA-1A) utilizes the VH4.21 gene.

Human IgM monoclonal antibody A6H4C5 was manufactured by Centocor (Malvern, PA) and used in clinical trials as HA-1A (Centoxin). In vitro, A6H4C6 binds to lipid A and rough-strain, gram-negative bacteria endotoxin. Further analysis of A6H4C5 has shown that it is a polyreactive, cold agglutinin that utilizes the VH4.21 gene segment in germline configuration. It is also a human antibody that binds to human B cells. We have characterized several other independently derived VH4.21 human monoclonal antibodies with the same characteristics as A6H4C5. This group of antibodies may represent a conserved host immune response.