Jean-Claude Jaton

Homogeneous Antibodies: Induction and Value as Probe for the Antibody Problem

Central issues of current immunology are the molecular basis of antibody specificity and the origin of antibody diversity. While it is clear that antibody specificity is a consequence of the amino acid sequence of the variable regions of light and heavy polypeptide chains of the immunoglobulin molecule, for which the methodology is straight forward (by the determination of the amino acid sequence and X-ray crystallography), the second problem still escapes direct attack. This question is referring to two points: (1) How did antibody diversity arise, and (2) How is antibody diversity maintained? The structural data available from immunoglobulins of different species, and the fact that low vertebrates, having less than 106 lymphocytes (Du Pasquier, 1970), i.e. a lower number of different variable regions, manage to cope with antigenic determinants known to date, appear to be in support of the view that antibody variability in vertebrates is achieved mainly by evolutionary processes (Hilschmann et al., 1970; Hood and Talmage, 1970; Hood and Prahl, 1971). The problem which we would like to discuss is: How is antibody diversity maintained in different species?

The aminoterminal sequence of antibody light chains: evidence for possible inheritance of structural genes.

Abstract Amino-terminal sequence analyses of 12 rabbit antibody light chains with restricted heterogeneity induced with either streptococcal group or pneumococcal type antigens are described. A comparison of their 27–30 N-terminal residue positions and comparison with the homologous regions of human and mouse κ chains suggest the following conclusions: 1. 1. Rabbit, mouse and human κ chains are homologous. They share the prototype N-terminal sequence Asp-Ile-Val-Met-Thr-Gln and predominantly or exclusively a number of residues further on in the N-terminal 27 position (e.g. Pro 9, Gly 17, Thr 21, Ile 22, Cys 24, Ala 26 and Ser 27). The protoype rabbit light chain sequence appears to start with Ala-Asp-Ile-Val-Met, and is thus longer by one risidue than human and mouse κ chains. Like their human and mouse couinterparts rabbits κ chains can be subgrouped. A minimum number of six subgroups is distinguishable on the basis of the current sequence information. 2. 2. The existence of species specific amino acid residues in the region reported appeats to be doubtful because positions 12 ans 18 are also found to be variable. 3. 3. Rabbit allotype b4 light chains show the greatest variations in the N-terminal 5 amino acid positions with the highest variability index in position 3. 4. 4. The degree of homology of antibody light chain N-termini appears to be a function of the breeding relationship of individual rabbits. For example, antibody light chains of a parent and an offspring rabbit with identical specilities were identical within their N-terminal 22 amino would imply inheritance of structural v-region genes for the synthesis of specific anti-polysaccharide antibodies.

Identical sequence of light chains from rabbit anti-streptococcal antibodies

CONSIDERABLE advances have been made with special breeding programmes in the selection of rabbits with amplified immune responses to polysaccharides specific for different streptococcal groups1,2. Levels of group specific antibodies of 50 mg ml−1 have been reported. Such antisera are valuable because they often contain monoclonal antibody which can be used in studies of the origin of antibody diversity. These antibody probes have stimulated a search for variable region markers common to antibodies specific for the same polysaccharide antigen3 and produced by closely related rabbits4,7. In a continuation of earlier marker analyses3 and of a breeding programme for restricted high responders8, we have used the streptococcal group A variant antigen (strain A486 variant of the Rockefeller University) to immunise part-inbred rabbits6,7. This cell wall polysaccharide is a homopolymer of rhamnose9,10 of very limited heterogeneity. We report the partial amino acid sequences of light chains of the b4 allotype isolated from monoclonal antibodies raised in six closely related rabbits after a primary or secondary course of intravenous immunisation with a streptococcal group A variant vaccine6.