Sensitivity of nested PCR-SSP typing for HLA class I alleles. (a) Primer mix (PM) 151 (A*0101-4N); (b) PM 9 (A*2501-2, A*2601-11N, A*3401-2, A*6601-3); (c) PM 155 (B*0801-3); (d) PM 47 (B*1301-3); (e) PM 86 (Cw*0102-3); and (f) PM 106 (Cw*1502-6). DNA of known HLA type (200 ng/μL) was mixed with an irrelevant DNA (200 ng/μL) to give relative final concentrations of 10% (lane 1), 1% (lane 2), 0.1% (lane 3), 0.01% (lane 4), and 0.001% (lane 5). Lane 6 is a specificity control in which the irrelevant DNA was amplified on its own. Each mix was then subject to a primary amplification with the appropriate set of first-round primers.28 The resultant product was diluted 1:500 in water before PCR-SSP typing using the method of Bunce et al.19 The gel is run from negative (−) to positive (+). Sensitivity experiments were performed on 3 occasions, and each primer mix was reproducibly capable of detecting DNA at a final concentration of 0.001%.