HLA and the sudden infant death syndrome

HLA phenotypes of 66 parents of 33 infants succumbing to the sudden infant death syndrome (SIDS) were determined using a standard microlymphocytotoxicity method. Heterogeneity testing over all locus antigens revealed a significant difference between the parents and a control group consisting of blood donors and healthy unrelated volunteers. This heterogeneity was still evident when maternal and paternal groups were considered separately with the controls and when compared with each other. Individual A locus antigens displaying frequency deviation from control values included A9 (decreased in husbands), A10 (increased in wives and total parent group), and A28 (increased in wives). The increase in frequency of A10 became highly significant when only parents of children with evidence of laryngitis at post mortem were used for comparison with control values. No difference in B locus antigens between any of the groups was observed. The results obtained are compatible with the view that SIDS is the result of a hypersensitivity reaction to one or more allergens and that genes coding for these specific responses are linked to the HLA complex. Differences observed between the maternal and paternal groups may be explained on the basis of maternal antibody, passively acquired by the infant, which serves a protective role in the respiratory tract, prior to the development of immunocompetence. The production of these antibodies is also dependent on genes linked to the maternal HLA complex.