44.
Amino acid sequence analyses were carried out on monoclonal anti-
p-azophenylarsonate antibodies isolated from the ascites of mice carrying cell lines obtained from the fusion of A/J splenic lymphocytes with the myeloma cell line Sp2/0–Ag14. The partial primary structures of both heavy and light chains from seven idiotype negative hybridoma proteins are compared to those of six idiotype positive molecules. Amino-terminal amino acid sequences (40–47 residues) of heavy chains from molecules bearing the major cross-reacting idiotype, Id
CR, demonstrated 95% homology to each other. Similarly, aminoterminal sequences of Id
CR+light chains were homologous to each other. However, sequence variations were evident in individual antibodies in both framework and complementarity-determining regions, suggesting that a large family of molecules accounts for the major cross-reacting idiotype, as previously reported (Marshak-Rothstein
et al., 1980
b).
Heavy and light chains from seven IdCR-negative monoclonal antibodies were subjected to amino-terminal (37–48 residues) amino acid sequence analysis. Four heavy chains were blocked to Edman degradation, but could be sequenced after enzymatic removal of the amino-terminal pyrrolidone carboxylic acid residue. In comparison with IdCR-positive heavy chains, the IdCR-negative heavy chains demonstrate greater diversity in both framework and complementarity-determining regions, with several different subgroups represented in contrast to the results from pooled serum IdCR-positive antibodies (Capra et al., 1975). One of the seven IdCR-negative light chains was blocked. The sequences of the remaining IdCR-negative light chains exhibited marked variations in both framework and complementarity-determining regions, with different chain lengths in the first complementarity-determining region in several light chains.
Comparisons between the amino-terminal sequences of IdCR-positive and IdCR-negative monoclonal antibodies suggest that specific sequences in the first complementarity-determining regions of both heavy and light chains are not sufficient to account for the major cross-reacting idiotype. The structural basis for IdCR in A/J mice is likely to be in other segments of the variable regions. 相似文献