Characterization of an Ig V(H) idiotope that results in specific homophilic binding and increased avidity for antigen Journal Article
| Authors: | Yan, X.; Evans, S. V.; Kaminki, M. J.; Gillies, S. D.; Reisfeld, R. A.; Houghton, A. N.; Chapman, P. B. |
| Article Title: | Characterization of an Ig V(H) idiotope that results in specific homophilic binding and increased avidity for antigen |
| Abstract: | mAb against GD3 ganglioside demonstrate homophilic binding in which soluble anti-GD3 mAb bind, through the GD3 binding site, to a VH idiotope (designated IdHOM) on solid phase anti-GD3 mAb. In this way, homophilic binding provides a mechanism for amplifying the binding of mAb to cell surface GD3. We show that serine 52a, within CDR2, is required for IdHOM expression, homophilic binding, and high avidity binding to cell surface GD3. Computer modeling based on the crystal structure of anti-GD3 mAb R24 showed serine 52a situated at the mouth of the GD3 binding pocket, but not directly involved with GD3 binding. Substitutions at position 52a predicted to maintain the GD3 binding pocket (e.g., threonine) resulted in the loss of IdHOM expression and homophilic binding and markedly decreased binding to cell surface GD3, but maintained low avidity GD3 binding as measured by ELISA. All other substitutions at position 52a were predicted to significantly distort the GD3 binding pocket and resulted in the loss of both homophilic binding and any detectable avidity for GD3. We have structurally defined IdHOM and conclude that this idiotope is not required for the GD3 binding pocket, but that the idiotope is necessary for homophilic binding, which is required for high avidity binding to cell surface GD3. We speculate that selection of certain VH genes may result in the expression of idiotopes that allow homophilic binding, and this may represent a general mechanism for increasing the avidity of Abs against T cell-independent Ags. |
| Keywords: | genetics; molecular genetics; protein conformation; mouse; animal; metabolism; animals; mice; biological model; pathology; tumor cells, cultured; gene vector; genetic vectors; monoclonal antibody; immunology; antibodies, monoclonal; chemistry; immunoglobulin heavy chain; immunoglobulin variable region; amino acid sequence; immunoglobulin heavy chains; molecular sequence data; sequence homology, amino acid; antigen; hybrid protein; antigens; recombinant fusion proteins; cell culture; sequence alignment; nucleotide sequence; experimental melanoma; melanoma, experimental; base sequence; models, molecular; mutagenesis, site-directed; chemical structure; sequence homology; site directed mutagenesis; antibody affinity; immunoglobulin m; binding sites, antibody; gangliosides; ganglioside; antigen-antibody reactions; models, immunological; antigen antibody reaction; antibody combining site; immunoglobulin idiotype; immunoglobulin idiotypes; humans; human; article; ganglioside, gd3 |
| Journal Title: | Journal of Immunology |
| Volume: | 157 |
| Issue: | 4 |
| ISSN: | 0022-1767 |
| Publisher: | The American Association of Immunologists, Inc |
| Date Published: | 1996-08-15 |
| Start Page: | 1582 |
| End Page: | 1588 |
| Language: | English |
| PUBMED: | 8759742 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | Article -- Export Date: 22 November 2017 -- Source: Scopus |
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