MAJOR HISTOCOMPATIBILITY COMPLEX GENES IN A MEXICAN FAMILY WITH DEFICIENCY OF THE 2ND COMPONENT OF THE COMPLEMENT-SYSTEM

Hereditary deficiency of the second component of the complement system is an uncommon condition that has been reported so far mostly in Cauc asians. We describe a Mexican patient with undetectable C2 levels and absence of complement hemolytic activity. Major histocompatibility com plex (MHC) genes in his family showed that the proband had the MHC hap lotypes HLA-A25, B18, DR2, DQ1, SQ042/HLA-A24, B18, DR2, DQ1, SQ042. A strong genetic linkage of the deficiency of the second component of t he complement gene and the HLA antigens A25, B18, and DR2, is well est ablished in Caucasian populations. This suggests that the probable ori gin of the deficiency in our patient was admixture with Caucasian ance stors.