RT Journal Article SR Electronic T1 Characterisation of a mouse monoclonal anti-idiotype reactive with a V region sequence commonly used by human immunoglobulins JF Molecular Pathology JO Mol Pathol FD BMJ Publishing Group Ltd and Association of Clinical Pathologists SP 77 OP 82 DO 10.1136/mp.53.2.77 VO 53 IS 2 A1 J E McElveen A1 P B Furtado A1 S J Smith A1 M R Clark A1 I Spendlove A1 H F Sewell A1 F Shakib YR 2000 UL http://mp.bmj.com/content/53/2/77.abstract AB Background—A mouse monoclonal antibody (2C7/IgG2bκ) has been described recently, which is directed against the major house dust mite allergen Der p 1, and whose epitope specificity is representative of a major component of the human IgE anti-Der p 1 response. Aims—To characterise an anti-idiotypic antibody (2G10/IgG1κ) raised against monoclonal antibody 2C7 as surrogate human IgE anti-Der p 1. Methods—The specificity of the anti-idiotype antibody 2G10 was determined by competitive inhibition experiments using human and mouse immunoglobulins of known VH gene families. The epitope recognised by monoclonal antibody 2G10 was located on the molecular model of the Fv (fragment variable) region of monoclonal antibody 2C7. Results—The data suggest that monoclonal antibody 2G10 is directed against a crossreactive idiotype on human IgE that is shared by polyclonal IgG. Competitive inhibition studies against human immunoglobulins, representative of VH2, VH3, and VH4 gene families, showed that monoclonal antibody 2G10 is mostly likely to be directed against sequences encoded by either VH3 or VH4 genes. The fact that monoclonal antibody 2G10 binds to the humanised (complementarity determining region (CDR) grafted) CAMPATH-1H antibody, but not to the original rat CAMPATH-1 YTH34.5.6 antibody, indicates that it is directed against a framework region rather than the CDRs. Analysis of amino acids in the VH region for charge, hydrophobicity, and accessibility suggests that reactivity with monoclonal antibody 2G10 is defined by a hexapeptide spanning residues 74–79 within framework region 3. Conclusion—The anti-idiotype monoclonal antibody 2G10 could potentially be used as a probe for determining the contribution of the VH3 and VH4 gene segments to antigenic specificity.