chromosome 6p close to the HLA genetic region (25,26).
Cazzullo and colleagues reported the first HLA-association
study of schizophrenia in 1974 (27). More than 60 association
studies have been reported since then. In the first review of
HLA and schizophrenia, in 1979, McGuffin commented that
theMHCwas a logical place to search for genetic markers for
schizophrenia (28). This was because schizophrenia subtypes
showed several similar attributes, such as familial nature, an
imperfectly understood etiology, and a postulated autoimmune
pathogenesis, for which HLA association had
already been established (29). Most of the previous studies on
the involvement of the HLA system in schizophrenia have
yielded inconsistent results because most considered schizophrenia
as a whole. An association between HLA-A24 and
schizophrenia has been reported (30). At least 7 studies have
shown HLA-A9 to be elevated in patients with paranoid
schizophrenia (31). Studies that divided HLA-A9 into subspecies
found associations between schizophrenia and both
HLA-A23 (32) and HLA-A24 (33). However, Alexander and
colleagues found no association between either HLA-A23 or
A24 and the paranoid subtype and expressed doubt about an
association between HLA-A24 and schizophrenia (34).