A human-human hybridoma antibody (TrB12) defining subgroups of HLA-DQw1 and -DQw3.

We have constructed an IgG, kappa human--human hybridoma Ab(TrB12), which precipitates a molecule consisting of two polypeptides of about 33 and 27 kD in size. TrB12 reacted with; (1) 7 out of 10 DQw1-positive cell lines in IIF, and all 10 in a rosette-assay; (2) 5 out of 12 DQw3-positive cells, both in IIF and the rosette-assay; (3) none of 4 DQw2 homozygous cells. Detergent cell lysate of DQw1 homozygous cell lines contained antigens that cross-linked the mouse monoclonal antibody Genox 353 G2a-5 (anti-DQw1) and TrB12. TrB12 competed with the mouse DQw3-specific monoclonal antibody IVD-12 for binding to DQw3 homozygous cells. The data imply that the TrB12 epitope is associated with molecules that carry DQw1 and DQw3 serological specificities. By radioimmunoassay, TrB12 and the mouse monoclonal antibody IIB3 divided both DQw1- and DQw3- bearing cell lines into three phenotypic groups: (1) TrB12+IIB3hi, (2) TrB12-IIB3lo, and (3) TrB12-IIB3-. For DQw1 the results suggest that the first two groups represent structural variants but the third group may reflect low expression of DQw1. For DQw3 the evidence suggests that all three phenotypes represent structural variants. DQw3 has previously been divided into two serologically defined alleles, TA10+IIB3- and TA10-IIB3+. The TrB12+IIB3hi and TrB12-IIB3lo variants of DQw3 described in this study probably represent novel subgroups of the TA10-IIB3+ allele.