MOLECULAR CHARACTERIZATION OF ANTIGENIC POLYMORPHISMS (OND(A) AND MART(A)) OF THE BETA(2) FAMILY RECOGNIZED BY HUMAN-LEUKOCYTE ALLOANTISERA

We show that the previously described alloantisera Ond and Mart, which recognize the alloantigens Ond(a) and Mart(a), react with polymorphic variants of alpha(L) and alpha(M) subunits of the beta(2) integrin fa mily (CD11a and CD11b molecules). This was shown by testing the alloan tisera in a monoclonal antibody-specific immobilization of leukocyte a ntigens, immunoprecipitation, and immunofluorescence assay against cel ls from normal donors and from patients with leukocyte adhesion defici ency (beta(2) integrin deficient). To elucidate the molecular basis of the Ond(a) and Mart(a) alloantigens, RNA was isolated from mononuclea r leukocytes derived from individuals of known serologic phenotype. Re verse transcriptase-polymerase chain reaction (RT-PCR) was performed t o amplify the entire coding region of the alpha(L) and alpha(M) mRNAs, The Ond(a) antigen was found to be due to a G2466C substitution in th e DNA coding for the alpha(L) subunit, which predicts an Arg766Thr ami no-acid polymorphism. The Mart(a) antigen was also found to be due to a single nucleotide substitution (G302A) in the DNA coding for the alp ha(M) subunit, which predicts an Arg61His amino acid polymorphism. Usi ng allele-specific restriction enzyme analysis, the association betwee n point mutations and phenotypes was confirmed. The localization of th ese alloantigens on integrin molecules further illustrates the polymor phic nature of this class of proteins. Whether the polymorphisms influ ence the adhesive capacity of the leukocyte integrins remains to be in vestigated. (C) 1996 by The American Society of Hematology.