Antigenicity of Xf Protein Components

SUMMARY The antigen-antibody neutralization of filamentous phage Xf showed first-order kinetics within the first 10 minutes. Failure to reverse the neutralization reaction by dilution indicated that a stable combination might be formed between phage and antibody. Antigenicity of Xf was analysed by agar double diffusion and three distinct precipitin lines were observed. For identifying these three antigenic components, Xf particles were dissolved and separated into A-protein and B-protein. The results of agar double diffusion showed that one precipitin line corresponds to the A-protein and the other two precipitin lines are determined by the B-protein.