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Selection for Polymorphism in the Antigen Recognition Site of Major Histocompatibility Complex Class II Molecules
Author(s) -
JONSSON A.K.,
ANDERSSON L.,
RASK L.
Publication year - 1989
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1111/j.1365-3083.1989.tb02444.x
Subject(s) - major histocompatibility complex , genetics , biology , exon , gene , antigen , homologous chromosome , microbiology and biotechnology
The genetic basis for the extensive polymorphism of major histocompatibility complex (MHC) class II molecules was investigated by statistical analysis. Nucleotide sequences of human DQA1, DQB1, DRB1, and DRB3 genes and murine Aα, Aβ, and Eβ genes were used. The results show that polymorphism is selected for in the antigen recognition site of class II molecules since replacement substitutions in this region were found to occur at a significantly higher frequency than expected in the absence of selection. In contrast, replacement substitutions are selected against in the remaining part of the first domain exon and in the second domain exon. Furthermore, comparing the sequence variability pattern among different class II α and β sequences, using a variability index for each residue, showed that, with few exceptions, highly polymorphic residues occur in the antigen recognition site. There was a strong and highly significant correlation in the variability pattern in the homologous DRB/Eβ sequences but not for DQB/Aβ or DQA/Aα sequences. This difference may be related to the fact that both α and β chains of DQ/A molecules are polymorphic, while only β chains of DR/E molecules vary.