Allotypes of Rabbit Immunoglobulins

Although many different allotypic groups are known in the rabbit, structural data on what constitutes the antigenic determinants are available (and, in most instances, only partially) only for the allotypes of groups a, b, d, e, f, g, and a negative (x and y). 

Group e allotypes have been correlated with a Thr (el4) to Ala (el5) interchange at position 309 of rabbit y chains (Appella et al., 1971). This difference was the only one found among tryptic peptides from the Fc region of el4 and el5 heavy chains. 

In early studies to determine the structural basis for allotypic specificities, Wilkinson (1969a,fe) isolated amino-terminal peptides from IgG 

Further sequence analysis by Mole et al. (1971) of pooled IgG heavy chains of either allotype al or a3 delineated additional areas for potential allotypic correlations (Todd, 1972). These were compared with the sequence of a homogeneous antibody of allotype a2 (Fleischman, 1971). These studies showed, when corrected for hypervariable sequences and group a negative molecules, that amino acid interchanges occurring at positions 4, 7, 9, 11, 12, 15, and 16 could be correlated with group a allotypes. In addition substitutions at positions 80-85 from the amino-terminal end of the heavy chain could also be associated with allotypic differences. 

Subsequent studies (Jaton et al., 1973) showed that not all of the differences in this region (positions 80-85) were allotype related. However, these investigators showed that interchanges at positions 84 and 85 were definite allotypic correlates. Allotype al molecules were shown to have a Thr-Glu sequence in this region, a2 molecules an Ala-Glu, and a3 molecules an Ala-Ala sequence. 

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