The Identification of HLA-A9 in Dried Stains of Blood and Body Secretions

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Abstract
Specific inhibition of two HLA-A9 antisera in a one-stage extraction-absorption adaptation of the classical microlymphocytotoxicity test was investigated using 161 bloodstains and 42 stains of body secretions. Readable results with two-week old bloodstains were 97.5% accurate for those containing A9 and 100% accurate for those lacking A9. Readable results with fifteen month old bloodstains were equally accurate but reduced to a success rate of 14% with positive stains. The A9 frequency in comparison blood samples from casework reflected that observed in the control panel of donors. In contrast to previous studies of A1, A2 and B5 antigens in which the reactions of two or three antisera in parallel were needed to establish the presence of an antigen in a dried bloodstain, the antisera in this study were sensitive to A9 in stains from each positive donor yet insensitive to cross reactive antigens. Both false positive and false negative results were obtained with 22 saliva stains but none of the known positives inhibited the antisera specifically. Twelve seminal stains were tested but only one out of four stains containing A9 inhibited the antisera. Preliminary investigations with stains of urine, perspiration and vaginal secretion were generally negative.