[Anencephalus immunogenetic factor].

The T/t complex in the mouse is considered to be a gene locus that brings about neural tube defects. This locus is found to exist near the H-2 complex, which is the MHC of the mouse. Accordingly, it is conceivable that there exists a T/t-like complex near the HLA complex in humans. Studies on the HLA-A, -B, -DR, -DRw52, -53 and DQ loci of parents with anencephalus and affected offspring were undertaken with the aim of revealing the relationship between anencephalus and the HLA complex. The following results were obtained: The gene frequency of HLA-DR5 in a mother with anencephalus was significantly higher than in controls. HLA-DR materno-paternal compatibility was significantly higher than in control couples. An increase in HLA-DR, -DRw52, -53 and DQ homozygosity were observed among the affected offspring. These results indicated that there may exist an anencephalus immunogenetic factor in the HLA-D region.