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The clinical importance of variation within the HLA-Bw4 complex
R W Collins1, A W Harmer, A J Heads
1South Thames Tissue Typing, NGH3, Guy's Hospital, St. Thomas Street, London, SE1 9RT, UK.
Background:
Antibody screening of a patient with a failed renal transplant showed positive reactions with most, but not all HLA-Bw4-associated B-locus antigens. However, the patient's serological HLA class I type suggested the presence of HLA-Bw4.
Methods:
Standard molecular techniques were used to re-type the patient and donor. ELISA antibody screening helped determine the patient's antibody specificity.
Results:
The patient's type was HLA-B*1402,4703;Bw6 and the donor HLA-B*4703,51011;Bw4,6. Analysis of ELISA results identified three amino acids (positions 77,80,81) as the most likely epitope recognised by the patient's serum. These corresponded to HLA-B*51011 amino acid mismatches, explaining the lymphocytotoxic reactivity pattern. This epitope is located on a subgroup of the HLA-Bw4 antigen suggesting anti-Bw4 was not a sufficient description of this antibody.
Conclusions:
This report identifies an antibody to a sub-group of the Bw4 public specificity and also confirms the need for sequence-level analysis in the tissue-typing laboratory to determine future unacceptable mismatches.