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

Immunoglobulin kappa light-chain diversity in rabbit is based on the 3' length heterogeneity of germ-line variable genes

Antibody diversity is generated by the combinatorial association of multiple distinct genetic segments (variable (V), joining (J) and diversity (D) light (L) and heavy (H) chains--VL, JL and VH, D, JH) and amplified somatically by three or four different mechanisms. The kappa system in mouse and human consists of 50-100 V kappa segments associated with a cluster of four or five functional J kappa segments, located 2.5 kilobases (kb) 5' to a single C kappa gene. The third hypervariable region (CDR3), which is part of the antibody combining site, is usually nine amino acids long in human and mouse kappa chains. It is encoded by the last seven codons of the V kappa segment and the first two of the J kappa segment, one codon sometimes being added or deleted between V and J by junctional variation. In the rabbit, the C kappa 1 gene which encodes the major isotype, is associated with a cluster of five J kappa segments, only one of which seems to be functional, thus significantly decreasing the combinatorial potential. However, amino acid sequence comparison has revealed extensive heterogeneity in the length of rabbit CDR3 , suggesting the existence of a D segment analogous to that in the heavy-chain system. We show here that rabbit V kappa genes have several additional nucleotides at their 3' ends. Thus, even with a single functional J kappa segment, high CDR3 diversity can be generated based on the length heterogeneity of V kappa germ-line segments and their greater length, which might leave scope for an increased junctional deletion.

An inherited restriction in the idiotypic variability as a possible explanation of a genetic predisposition for a monoclonal component

Genetic factors have been proposed to play a role in the aetiology of a monoclonal proliferation of B lymphocytes. As an additional genetic factor we postulate that a restriction in the idiotypic variability of an individual contributes to a genetic predisposition to monoclonal gammopathy. To support our hypothesis, we have examined three families with multiple occurrence of M-components for sharing of idiotypic antigenicity between the related M-components and between the M-components and the sera of unaffected relatives. Idiotypic antisera against five isolated M-components were raised in guinea-pigs and used in a radiobinding inhibition assay. In none of the three families was idiotypic cross-reactivity observed between the familial M-components. However, in a family with three members with an M-component, sera of first-degree relatives showed a higher inhibitory capacity than sera of non-related individuals when an idiotypic antiserum, raised against the M-component of proposita, was employed. Within this particular family the observed restriction in the idiotypic variability could have contributed to the multiple occurrence of M-components.

The VkVI subgroup of rabbit light chains: complete amino acid sequence of a third variable region (K29-213)

The amino acid sequence of the variable region of a rabbit anti-streptococcal A-variant antibody light chain was determined. By using a combination of different cleavage methods, the sequence was established. Large peptides were sequenced in an extensively modified Beckman sequentor. Light chain K29-213 belongs to a rare subgroup (kVI). Several of these light chains of antibodies with different specificities have been totally or partially sequenced. Comparison of these light chains reveals at least four germ-line-encoded variants within this subgroup.

Structural restriction and similarities of the light chains of antibodies to group B streptococcal carbohydrate produced in a single rabbit

Comparison of the amino acid compositions, N-terminal amino acids and tryptic peptide maps of two L chains (145 LI and 145 LII) derived from antibodies produced in a single rabbit to group B streptococci indicates a high degree of sequence homology of the two chains. Furthermore, comparison of these data with similar analysis of L chains prepared from pooled antibodies to group B streptococci indicates a high degree of V region restriction in the L chains of antibodies elicited by hyperimmunization with streptococci.

Peptide mapping of the lambda-like chains of the BASILEA rabbits

The recently established mutant strain of rabbits, named BASILEA, lacks the k polypeptide L-chain which is replaced by a lambda-like type (bas). This is evident from the amino acid composition and peptide maps of the bas L-chain when compared to the L-chains of the rabbits suppressed for the expression of the b locus allotypes.

Evidence for quasi-silent germline genes coding for phylogenetically ancient determinants of the rabbit a locus allotypes

Anti-a2 sera raised in a3 rabbits are shown to detect determinants on a2 molecules which are different from those detected by anti-a2 sera raised in a1 animals. The former determinants are occasionally observed at a low level in rabbits of the a1 allotype and at a high level in sera of Leporidae of different genera. The two types of anti-a2 sera are shown to compete for the same sterical region of the a2 molecules. All homogeneous a2 molecules which have been tested show both types of determinants.

Active heterologous chain recombinants of monoclonal antibodies raised in related rabbits

Heterologous chain recombinants of homogeneous anti-streptococcal group A-variant polysaccharide antibodies produced by pedigreed rabbits regain in certain pairs the same antigen-binding capacity as the homologous pairs. In contrast, chain recombinants with antibodies from nonrelated rabbits are much less active. This data suggests random pairing of immunoglobulin heavy and light chains coded for in the germ line and subsequent selection.

Rabbit antibody light chains: selective breeding narrows variability in framework and complementarity-determining residues

The amino acid sequence of 5 light (L) chain (b4) variable (Vl) regions and the partial sequence of VL (kappa) regions from 12 anti-streptococcal group A-varant polysaccharide (Av-CHO) and 2 anti-streptococcal group C polysaccharide (C-CHO) antibodies was determined. These sequences contain 70 invariant positions as opposed to 50 invariant positions in other rabbit VL regions. Variability within the framework residues lacks randomness, and parent offspring relationship or otherwise close familial relationship is apparent in several instances. Variability in the complementarity-determining regions is reduced by 2.3-5.5-fold in comparison with other rabbit L-chains with several identical first and third hypervariable regions. Residue positions 50-56, known to mark the second hypervariable region in human kappa-chains, are not hypervariable in L-chains from Av-CHO rabbit antibodies. Considering the 67 rabbit L-chain sequences, completely or partially known today, for counting the number of V region germ line genes, it is concluded that the species rabbit has at least 27 VL germ line genes available.

Partial amino acid sequences of kappa-chains of rat immunoglobulins: genetic and evolutionary implications

Partial amino acid sequences have been determined for several kappa-type light chains prepared from sera or urine of inbred LOU/C/Wsl rats bearing plasma cell tumors. Comparison of these sequences with those of human, rabbit, and mouse kappa-chains available in the literature indicates that the constant region of rat kappa-chains shows more amino acid sequence homology to that of the mouse kappa-chain than to human and rabbit kappa-chains, a result expected from the phylogenetic relationship of the species compared. Examination of the N-terminal amino acid sequences indicated that the variable regions of rat kappa-chains can also be classified into subgroups according to degree of sequence homology in a manner similar to that done for kappa-chains of other species (e.g., human, rabbit, and mouse). However, the prototype amino acid sequences of kappa-chain variable region subgroups of the rat were not homologous to those of other species including the closely related mouse. The implications of this observation with respect to the genetics and evolution of immunoglobulins are discussed.

Sequence variability of rabbit antibody light chains. Familial occurrence of n-terminal sequence differences between b4 and b9 light chains

Amino acid sequence analyses of the IgG light (L) chains from selected members of a rabbit family with allotypes b4 and b9 showed N-terminal substitutions that segregated with the b4 allotype. The L chains of allotype b4 had tyrosine at step 2, whereas this residue was absent from that step in the b9 L chains. Steps 12 and 13 of b4 L chains yielded a high percentage of glutamic acid, whereas a low percentage was observed for the b9 L chains. These tyrosine and glutamic acid substitutions were observed with the same frequency in L chains from homogeneous antibodies as in the L chains of the IgG samples. The data suggest that, in the family studied, separate and distinct V-region gene complexes are linked to the b4 and b9 allotypic genes.

Antigen binding and idiotypic properties of reconstituted immunoglobulins G derived from homogeneous rabbit anti-pneumococcal antibodies

Recombinations and hybridizations of H and L-chains derived from several homogeneous rabbit antibodies to type 3 pneumococcal polysaccharide (SIII) were carried out. All reconstitution experiments performed gave rise to genuine IgG molecules. Antigen-binding studies and affinity measurements for a hexasaccharide ligand derived from SIII were made. In addition, heterologous antiidiotypic serum raised against one rabbit anti-SIII antibody was used to measure the reconstitution of idiotypic determinants in hybrid immunoglobulin molecules. The results show that full recovery of the antigen-binding properties was obtained only when chains derived from the same antibody molecules were reassociated. Similarly, the complete regain of idiotypic determinants (studied in one antibody system) could only be demonstrated in the homologous recombinants. The pairing of an H-chain with several heterologous L-chains, which differed in 6-11 positions in the 3 hypervariable sections, led to the formation of hybrid IgG molecules which had an affinity at least 100-fold lower than that of the parent anti-body molecule and a number of hapten-binding sites which did not exceed 0.30.

Rabbit immunoglobulin allotypes: structure, immunology, and genetics

Over a 6-month period, 157 patients, 89 of whom had central nervous system tumors, were examined on a prototype 0.12 T resistive nuclear magnetic resonance (NMR) imaging unit. All of the patients had computed tomography (CT), which was used as a standard to which the NMR findings were compared. Studies were done primarily by saturation-recovery technique with short repetition times. The signal intensity with saturation-recovery technique did not allow differentiation among most tumor types. Location, extent, and morphology helped to some extent in attempts at differentiation. In the multiplanar mode, NMR compared favorably to CT with regard to lesion detection. Limited early experience suggests that NMR also may detect some lesions when the CT is negative and may detect additional lesions when one or more are present. The NMR examination was well tolerated by selected patients.

Completion of the analysis of the primary structure of the variable domain of a homogeneous rabbit antibody to type III pneumococcal polysaccharide

The amino acid sequence between residues 70 and 116 of the V (variable) region of the H (heavy) chain derived from rabbit antibody BS-5, specific for type III pneumococcal polysaccharide, was determined. The sequence of this section of the H chain which includes the hypervariable residues 94 to about 112 was unique, although minor variant sequences present in the H chain preparation would not have been detected by the techniques used in this work. Taken together with the known sequences of the N-terminal 69 residues of H chain BS-5 (Jaton & Braun, 1972) and of the V region of the light chain (Jaton, 1974b), the data establish the complete sequence of the V domain of a rabbit immunoglobulin G. The V region of H chain BS-5 is compared with the basic sequences of the three human V region subgroups known to date, with one mouse H chain, and with guinea-pig pooled H chains. Even though chains from guinea pig and mouse clearly belong to the subgroup III of variability (V(HIII)), rabbit H chain BS-5 (allotypic variant a(1)) appears more closely related to the subgroup V(HII) than to the subgroups V(HIII) or V(HI). The homology between V(L) and V(H) regions of antibody BS-5 (28%) is not greater than that observed between the V(H) region of antibody BS-5 and the V(L) regions of different rabbit antibodies.

Amino acid sequence of the N-terminal 139 residues of light chain derived from a homogeneous rabbit antibody

The amino acid sequence of the N-terminal 139 residues of the L (light) chain derived from a homogeneous rabbit antibody (designated BS-1) to type III pneumococci was determined. A combination of methods involving tryptic cleavage restricted to the 2 arginine residues of the molecule and mild acid hydrolysis of a labile peptide bond between the V (variable) and C (constant) regions of the L chain (Fraser et al., 1972) allowed the isolation of two large peptides comprising the entire V region (residues 1-109); these peptides were suitable for automated Edman degradation. The complete sequence analysis of the V region was carried out with only 4mumol of L chain. This material was homogeneous, although minor variant sequences, if present at the 10% value, would not have been detected. The L chain contains 3 intrachain disulphide bridges, whose pairing was established by diagonal electrophoresis: there is one V-region bridge between positions 23 and 88 and one C-region bridge between positions 134 and 194; the third one connects V and C domains between positions 80 and 171. When compared with the basic sequence of human kappa chains, rabbit L chain BS-1 appears to be more similar to the V(KI) prototype sequence than to V(KII) or V(KIII) sequences, where V(KI), V(KII) and V(KIII) represent subgroups I, II and III respectively of V regions of kappa light chains. The V regions of rabbit heavy and light chains are homologous to each other. The presence of two clusters of 3 glycine residues in positions 94-96 and 99-101 respectively is remarkable. Residues 94-96 may be related to antibody complementarity whereas residues 99-101 function probably as a pivot permitting the combining region of the L chain to make optimal contact with the antigenic determinant (Wu & Kabat, 1970).

Comparison of the amino acid sequences of the variable regions of light chains derived from two homogeneous rabbit anti-pneumococcal antibodies

The amino acid sequence of the N-terminal 139 residues of the L (light) chain derived from a homogeneous rabbit antibody to type III pneumococci was determined. This L chain, designated BS-5, exhibits a greater degree of homology with the basic sequence of human kappa chains of subgroup I (72%) than with subgroups II and III. L-chain BS-5 differs from another L chain (BS-1), also derived from an antibody to type III pneumococci (Jaton, 1974), by eight amino acid residues, even though the chains are identical within the N-terminal 30 residues. Six of these eight substitutions are located within the three hypervariable sections of the variable half: Asn/Ser in position 31, Glu/Ala in position 55, Asx/Thr, Thr/Gly, Thr/Gly and Val/Tyr in positions 92, 94, 96 and 97 respectively. The two anti-pneumococcal L chains BS-1 and BS-5 are much more similar to each other than to an anti-azobenzoate L chain (Appella et al., 1973), from which they differ by 30 and 29 residues respectively. Of these interchanges 13-15 are confined to the three hypervariable sections, and 11 occur within the N-terminal 27 positions. The three chains have an identical sequence from residue 98 to residue 139, except for a possible inversion of two residues in positions 130-131 of the anti-azobenzoate chain.

Partial amino acid sequence in the N-terminal region of an anti-pneumococcal immunoglobulin heavy chain of allotype alpha2

The amino acid sequence of the N-terminal 48 residues of the heavy chain derived from a homogeneous rabbit antibody to type III pneumococci is described. This chain of allotype a(2) is compared with other rabbit heavy chains of allotypes a(1), a(2) and a(3). Within the N-terminal 25 positions, two chains which carry the same allotype a(2) possess identical amino acid sequences, but differ markedly from heavy chains of allotypes a(1) and a(3). Sequence variability is observed in residues 26-27 and 30-34, but not in residues 35-48.

Idiotypic specificity of rabbit antibodies to streptococcal group polysaccharides

Anti-idiotypic antisera against six restricted rabbit streptococcal group specific antibodies have been raised in rabbits matched for allotypes. All these antisera reacted specifically with their homologous idiotypes on double-diffusion tests in agarose gel. In addition, they showed a high incidence of cross-specificities with group-specific hyperimmune sera induced in both closely related and unrelated individuals. These precipitating cross-specificities could be explained for two systems by the interference of rheumatoid factor. Two idiotypic antibody systems have been analyzed in detail; these were restricted antibodies produced in a father and in one of his offspring. The methods employed included binding inhibition of radio-labeled homologous Fab fragments and hemagglutination inhibition with homologous idiotypic coat. The data demonstrated that only related rabbits produced, besides non-cross-reacting antibodies, idiotypically similar antibodies raised to the same antigen. About one-third of the cross-reactive idiotypes showed binding inhibition between 31 and 92%. Inhibition of binding above 50% in the paternal idiotypic system was only achieved by one offspring antibody whereas the F(1) progeny idiotypic system was inhibited to this extent by seven antibodies of related rabbits. In contrast, 87.5% and 91.7% of antibodies of unrelated rabbits were less than 20% inhibitory. Within this study two idiotypically identical antibodies have not been found. This implies that A-variant-specific antibodies of related rabbits which produced antipolysaccharide antibodies were structurally different. Cross-reaction, even if greater than 90% by binding inhibition, appears to involve only part and not all of the variable regions.

A rabbit family of restricted high responders to the streptococcal group A-variant polysaccharide. Selective breeding narrows the isoelectric focusing spectra of dominant clones

Immunization of rabbits from a closed colony with streptococcal Group A-variant vaccines identified about two-thirds of them as low and heterogeneous responders. One-third of the rabbits showed a restriction of the response independent from the magnitude. Selective breeding from one monoclonal high-responder male and two restricted high-responder female rabbits succeeded in segregation of high-responder progeny after two generations. Their antibody levels were on the average 2.5 times higher than those of the random group of rabbits and a small group of low-responder offspring. Immunization of 13 offspring originating from rabbits bred for restricted high response to the streptococcal Group C polysaccharide revealed that 11 progeny were restricted high responders and 2 progeny monoclonal high responders. This finding suggests that high responsiveness to the Groups A-variant and C polysaccharides is inherited as genetically linked traits. Selective breeding combinations between restricted and monoclonal high-responder rabbits by brother-sister matings succeeded in narrowing the isoelectric focusing spectra of Group A-variant-specific antibodies in the offspring. It furthermore revealed a preferential expression of monoclonal antibodies after three generations with a similar net charge as those identified first in the original monoclonal paternal parent. These data suggest that similar copies of structural genes for the variable regions are transmitted from the parent to the progeny.