Immunogenetic determinants of familial acute lymphocytic leukemia.

Acute lymphocytic leukemia developed almost simultaneously in two adolescent brothers, and another brother and both parents had rheumatoid arthritis. Laboratory studies uncovered no evidence for an underlying immunodeficiency state in the family. Immunogenetic evaluation showed the leukemic siblings to be HLA- and mixed-leukocyte-culture identical and homozygous for a recessively inherited locus dictating the presence of antigens on the surface of B-cells. This Ia antigen, as detected by sera from mothers of leukemic children, appeared to be mapped within the major histocompatibility region and may be a human analogue to murine immune-response antigens associated with susceptibility to leukemia.