MOLECULAR CHARACTERIZATION OF G2M(N-) ALLOTYPES() AND G2M(N)

Immunoglobulin (Ig) allotype typing is usually performed with serologi cal methods based on hemagglutination inhibition. The recent developme nt of molecular techniques has allowed the molecular typing of several Ig markers. The hinge, CH2, and CH3 domains of the G2 gene from six u nrelated individuals (three G2m(n+) and three G2m(n-)) were amplified and cloned to establish the molecular basis of the G2m(n+) and G2m(n-) . Comparison of the allele sequences revealed three changes: two (codo ns 308 and 437) are silent exonic substitutions, one is a G to A trans ition corresponding to an amino acid difference in position 282: Val ( GTG) in G2m(n-), Met (ATG) in G2m(n+). These substitutions were identi fied via two approaches: 282 polymorphism, after digestion of a specif ic polymerase chain reaction product with Nla III followed by acrylami de electrophoresis; 308 and 437, by a dot-blot technique using allele- specific oligonucleotides. These molecular typing results correspond e xactly to those obtained serologically; moreover, the three substituti ons defining the G2m(n+) and G2m(n-) alleles are always associated in a strict linkage disequilibrium.