Light chains allotypes

A number of experiments have been reported by Bell and Dray (1969, 1970, 1971a, b, 1972, 1973) in which the authors describe conversion of non-immune rabbit spleen cells by RNA from immunized rabbit to produce IgM and IgG of donor light chain allotype. Furthermore, spleen cells from non-immunized rabbits were converted to antibody-forming cells by incubation with RNA extracts of lymph node cells obtained from rabbits immunized with SRC. If the RNA was extracted from lymph nodes of rabbits immunized 5 days previously, IgM anti-SRC antibody-forming cells were produced, while if the donor of RNA was immunized 18 to 24 days previously, IgG anti-SRC antibody-forming cells were detected in the converted spleen cells. 

Bell,C., Dray, S. Conversion of non-immune spleen cells by ribonucleic acid of lymphoid cells from an immunized rabbit to produce yM antibody of foreign light chain allotype. J. Immunol. 103, II96-I211 (1969). 

Bell, C., Dray, S. Conversion of homozygous lymphoid cells to produce IgM antibodies and IgG immunoglobulins of allelic light-chain allotype by injection of rabbits with RNA extracts. Cell. Immunol. 5, 52-65 (1972). 

In 1963, shortly after the four-chain model for immunoglobulins was proposed, Dray and Nisonoff showed that immunoglobulin molecules from rabbits heterozygous for allotypic determinants at a light chain locus contain either light chains of one allotype, or of the other, but not both. These authors did not interpret the results... 

The X light chains have been shown to express a number of antigenic determinants which also reflect isotypic differences (Fett and Deutsch, 1975). Two distinct antigenic types of human X chains, termed Oz" and Oz , were originally thought to be allotypic markers (see below) but were later shown by genetic analyses to be isotypic in nature. Both types of chain are thus found in all normal individuals. The structural correlate... 

As yet, allotypic markers on human X light chains and the heavy... 

Differences in carboxyl-terminal peptides (positions 210-214) have been correlated with group b allotypes (Frangione, 1969 Appellant aL, 1969). Light chains with the b4 allotype have the sequence Asn-Arg-Gly-Asp-Cys here, while b5 molecules have aS r-Arg-Ly -A jc-Cys sequence, and b6 molecules a Ser-Arg-Lys-Ser-Cys sequence in this region. The italicized residues are where b5 and b6 molecules differ from b4. The b4 molecules differ from human k chains only at position 213, where the human molecule has a Glu. The b9 molecule is identical to b4 chains in this region (Goodfleisch, 1975). 

Since most rabbit k chains have been identified either by amino acid sequence analysis or by their reactivity with anti-b-specific allotype sera, it is not known whether purely K-specific determinants (distinct from allotype-specific determinants) exist in these chains. To the authors knowledge, there has never been a report of a reaction between any k-specific antiserum and rabbit light chains. Very likely, it has not yet been looked for seriously. 

Fig. 4.12. Amino acid sequences and sites of enzymatic cleavage in the hinge regions of human and rabbit-y chains. The symbol H represents the site of an interheavy chain disulfide bond and the symbol L designates the site of a heavy-light chain disulfide bond. The halfcystine at position 220 of the rabbit y-chain forms an intrachain disulfide loop with Cys 131 or 132. The Eu numbering system is used (2). Pap, Pep, and T refer to cleavage sites for papain, pepsin, and trypsin, respectively. The site of cleavage of the rabbit H chain by papain is that for molecules of allotype dll. Hydrolysis by papain of molecules of allotype dl2 is described in the text. Cleavage of the rabbit H chain by trypsin at position 220 occurs only after reduction and aminoethylation (by ethyleneimine) of Cys-220. The symbol CHO represents carbohydrate. References are given in the legend of Fig. 4.9.

Allotypic specificities are, in all probability, determined by amino acid sequences. Thus, there are characteristic and reproducible differences with respect to the average amino acid composition of normal L chains of allotypes b4, b5, and b6. Light chains of allotypes b4 and b5 differ with respect to content of aspartic acid, threonine, arginine, serine, proline, valine, and leucine no differences are evident in the overall content of other amino acids. The average number of residue differences per... 

Light chains of allotypes b4, b5, and b6 can also be distinguished by peptide mapping (67,68) despite the heterogeneity of the chains, attributable to their V regions, certain peptide spots are characteristic of each phenotype. 

A third, and most definitive method for observing persistence is the analysis of amino acid sequence the idiotype of a molecule must be defined by sequences in the variable portions of its H and L chains. Amino acid sequence analysis has been used to observe the persistence of molecules of related or identical structure during repeated immunizations with type VIII pneumococcal vaccine (71). A rabbit received three 1-month courses of immunization with a rest period of 1 month after each course. Antibodies isolated after successive courses are referred to as Ab-1, Ab-2, and Ab-3. Specifically purified Ab-2 was homogeneous by the criterion of electrophoresis. Antiidiotypic antiserum specific for this purified antibody also reacted, although not as strongly, with Ab-1 and Ab-3. Light chains of Ab-2 were found to have a unique sequence for the first N-terminal 21 residues. This contrasts with nonspecific L chains of the same allotype (b4) which have multiple residues at many... 

The first attempt to suppress the synthesis of Ig allotypes in mice was unsuccessful. The majority of progeny from immunized mice mothers died, and surviving offspring demonstrated a normal concentration of the paternal allotype. However, Herzenberg successfully suppressed Ig synthesis with Ig-lb specificity, initially for short periods of time and then for the entire life of the mouse (Herzenberg, 1970). Recently, short-term suppression of Ig synthesis in mice was induced with the aid of antibodies to some of the determinants of the variable part of light polypeptide chains (Ruffmi et al., 1970). 

---