Status of an unpaired thiol group on the HLA-B27 epitope.
Sequence analysis and site-directed mutagenesis of HLA-B27 indicate an unpaired cysteine at position 67 of the hypervariable region corresponding to its serologically defined, disease-associated epitope. We investigated whether chemical modification of this thiol group affected the serological reactions of B27. B27-positive cells were treated with thiol-blocking agents and then tested for recognizable B27 expression. Anti-HLA-B27 alloantisera and monoclonal antibodies were used in cytotoxicity, absorption, and cellular ELISA (cELISA). The semi-quantitative cytotoxicity-based assays showed some decrease in both B27 and controls. However, cELISA indicated that the inhibition of B27 was significantly greater than control antigens, and dependent on thiol-blocker concentration. This suggests that a proportion of HLA-B27 molecules have a free, reactive thiol at the antibody-defined epitope. Incomplete inhibition by thiol-blocking agents indicates that the remainder are inaccessible.
McLean
L
L
London Hospital Medical College, England.
Perrett
D
D
Winrow
V R
VR
Archer
J R
JR
D000911:Antibodies, Monoclonal / Q000276:immunology; D003545:Cysteine / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology*; D015796:HLA-B27 Antigen / Q000276:immunology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects; D013438:Sulfhydryl Compounds / Q000276:immunology*; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D000939:Epitopes; D015796:HLA-B27 Antigen; D013438:Sulfhydryl Compounds; D013439:Sulfhydryl Reagents; D003545:Cysteine