Monoclonal Antibodies Reveal the Structural Basis of Antibody Diversity

Abstract

Hybridoma technology has made it possible to introduce into continuous culture normal antibody-forming cells and to obtain large amounts of the immunoglobulin produced by each of these cells. Examination of the structure of a number of monoclonal antibodies that react with a single antigen has provided new information on the structural basis of the specificity and affinity of antibodies. Comparisons of families of monoclonal antibodies derived from a single germ line gene revealed the importance of somatic mutation in generating antibody diversity. Monoclonal antibodies that react with variable regions of other monoclonals allow the further dissection and modulation of the immune response. Finally, the continued somatic instability of immunoglobulin genes in cultured antibody-forming cells makes it possible to determine the rate of somatic mutation and to generate mutant monoclonal antibodies that may be more effective serological reagents.

Construction of an extended three-dimensional idiotope map by electron microscopic analysis of idiotope-anti-idiotope complexes.

“…This is consistent with the observation that Id-specific amino acid substitutions tend to be clustered in the hypervariable regions (9)(10)(11)(12) and, as such, derive from the same diversity-generating mechanisms that lead to Ag-binding diversity (13,14). Examples of Id-anti-Id reactions that are not hapten inhibitable have also been reported (15).…”

Cytoskeletal binding of monoclonal anti‐dna antibodies derived from tonsillar lymphoid cells of a normal subject

“…This polyspecific binding of subclones KIM 7.2.4 or B11.5.1 could reflect the emergence of mutant clones arising from a single cell during clonal expansion in vitro. Such mutations occur frequently, as has been reported by Teillaud e t al (23). If indeed m u t a n t s of KIM 7.2.4 a n d B 1 I .5.…”

Somatic mutation of the T15 heavy chain gives rise to an antibody with autoantibody specificity.

“…Because many of the questions about somatic mutation are difficult to answer in vivo, where selection and regulation of expression are occurring, we have been examining the genetic instability of heavy chain V region genes in cultured myeloma cells (2). This somatic cell genetic system seemed particularly suited for determining the rate at which base changes occur and whether somatic mutation also generates antibodies that have lost the ability to react with the immunizing antigen.…”

“…Although it is clear that somatic mutations play a major role in generating antibody diversity (1,2), it has not been determined whether this is a random process, generating antibodies with increases and decreases in affinity for the eliciting antigen. If antibodies that have lost the ability to bind antigen do emerge, it is not known whether they acquire reactivity for other antigens or are just wastage.…”

“…This observation prompted us to examine the reactivity of antibodies we had derived by somatic mutation in tissue culture from the S107 myeloma cell line (2). S107 produces an IgA K-chain P-Cho binding antibody that is identical in its sequence to the T15 (V1) germ line heavy chain V region sequences (8).…”