The Detection of the HLA-A1 Antigen in Bloodstains

Abstract

The wealth of antigens in the HLA white cell blood group system makes their detection in bloodstains a fascinating possibility for the forensic serologist. The work presented in this paper is concerned with the detection of the HLA-A1 antigen in bloodstains. The essence of the technique employed is the inhibition of the lymphocytotoxic activity of anti-HLA-Al antisera by HLA-A1 bearing bloodstains. A 4 cm length of bloodstained thread was used for each test and incubation with the HLA antisera was overnight at 4°C. An inhibition of the cytotoxic activity of the HLA-A1 antiserum of 55–100 per cent was taken as indicative of the presence of the HLA-A1 antigen in the stain, while an inhibition of 0–45 per cent indicated the absence of the antigen. Inhibitions in the range 46–54 per cent were regarded as indeterminate. Three antisera were used in parallel as these produced more satisfactory results than those of a single antiserum. The HLA-A1 antigen appeared to show little loss of activity in stains up to 230 days old. The additional finding that whole blood samples could be successfully typed for the HLA-A1 antigen using this inhibition technique is of particular importance because, in forensic casework, fresh blood samples taken into the media ideal for normal HLA typing may not always be available. Lawyers should take note that, although the HLA system promises to be of great value in forensic problems, owing to the highly specialized nature of the techniques employed it will not be immediately applicable to routine case-work.