Measles, histocompatibility leukocyte antigen polymorphism, and natural selection in humans

Profound lymphocytopenia (greater than 2,000 lymphocytes/mm3) occurring within two days of rash in 69 South African black children with measles predicted either death or progression to chronic lung disease in 51 (77%) of 66 children who were followed for at least six weeks. Lymphocytopenia was significantly associated with the presence of histocompatibility leukocyte antigen (HLA) AW32 (P = 0.01), with a relative risk of 5.5. There was a trend toward an association between the presence of particular antigens in the HLA complex and the various indices of humoral and cellular immunity studied. These findings are discussed in terms of variation in the clinical spectrum of the disease and in relation to the evolution of HLA polymorphism.