Phylogenetically Associated Residues Within the Vhiii Subgroup of Several Mammalian Species

Abstract

The origin of the amino acid sequence diversity characteristic of the variable (V) regions of immunoglobulins has been the subject of considerable controversy for several years. Two types of theories have been proposed to account for this diversity, primarily on the basis of sequence data derived from light chains. "Pauci-gene" theories assume that there are relatively few variable region genes in the germ llne and that the many different variable region sequences required for the humoral antibody response are generated by some somatic process (1-4). Multi-gene, or germ line, theories assume, alternatively, that a full complement of variable region genes exists preformed in the germ line (5, 6). A clear choice between a pauci-or multi-gene theory will probably have to await direct analyses of lymphoid cell DNA. However, RNA hybridization studies that have been carried out to date (7, 8) have not settled the question unambiguously.Major challenges to the validity of multi-gene theories are their difficulty in explaining the origin and stability of the allotypic markers present in the variable regions of rabbit heavy chains and the finding of "species-specific residues" in immunoglobulin light chains (9). Completely satisfactory explanations of these features of ilnmunoglobulin structure have not yet been provided under multi-gene assumptions.The exact identity and distribution of the species-specific (or phylogenetically associated, ref. 10) residues have not been easy to determine because of the several variable region subgroups that are characteristic of the light chains of most species. The presence of the subgroups makes difficult the identification of such residues in pooled light chains from a single species, an approach that would be of enormous value in establishing their true significance.Previous studies of heavy chains prepared from myeloma proteins have shown that the primary structure of the variable region of proteins in the V n m subgroup is extremely conserved in at ]east four species, and that phylogenetically

Circulating immune complexes detected by 125I-Clq deviation test in sera of cancer patients.

“…However the amount of immune complexes was widely scattered. In several cases the levels of immune complexes were as high as those seen in sera of 10 patients studied with active systemic lupus erythematosus.…”

“…Our experience demonstrates that it is critical that these samples be used for determination of immune complexes within 2 wk and that they not be thawed at intervals. (10). The aggregation of IgG was carried out according to previously described methods (11 (14).…”

The structure of immunoglobulin variable regions in the horned shark,Heterodontus francisci

“…Since the analysis was carried out on normal immunoglobulin, and not on myeloma proteins or specifically elicited homogeneous antibodies, it was essential to determine the proportion of the available chains that was actually sequenced (i.e., to determine the proportion, if any, of polypeptide chains possessing blocked amino-terminal residues). This was done by determining the yield of certain internal residues relative to the total amount of protein sequenced (Capra et al 1973). The results show that for both the heavy and the light chains, more than 90% of the available polypeptide was sequenced.…”

Structural Studies of Induced Antibodies with Defined Idiotypic Specificities

“…Amino acid sequencing procedures. Samples of 5-7 mg of H chain were sequenced for 40 cycles in a Beckman 890C sequencer (Beckman Instruments, Palo Alto, Calif.), using a dimethylallylamine program with systems previously described from this laboratory (6,11). After conversion to phenylthiohydantoin (PTH) amino acids, identification was by gas chromatography, thin-layer chromatography (30) using BBOT (Packard Instruments, Downers Grove, 111.)…”