Molecular typing for the MHC with PCR-SSP.

Sequence-specific amplification (SSP) is simply a form of polymerase chain reaction (PCR) which involves designing one or both primers so that they will or will not allow amplification (the 3'-mismatch principle). Its origins are probably legion, i.e. many people probably thought of it at the same time. For example, in 1988 a group from Guy's Hospital, London, described a form of SSP for HLA-DR4 detection and in the same year a group from Upjohn described its use at the American Society of Histocompatibility and Immunogenetics (ASHI). Both are published in abstract form (British Society of Rheumatology and ASHI). The 3'-mismatch principle can be used to identify virtually any single nucleotide point mutation (SNP) within one or two PCR-SSP reactions and the first peer-reviewed statements of this came in 1989 (1, 2). Thus, although the use of SSP probably began around 1990, it was 5 years before its popularity erupted, mainly due to the work of Olerup & Zetterquist (3, 4), who defined its potential for solid organ transplantation. It is now the method of choice for high resolution HLA typing in many laboratories. In addition, over a thousand applications for genes outside the MHC are in the literature.