A new homozygous typing cell with HLA-D"H" (DB6) specificity. Evidence that the DN-1 monoclonal antibody 9w925 is specific for the HLA-D"H" determinant.

A new homozygous typing cell (HTC), SK is described. Mixed leukocyte culture (MLC) showed that SK is homozygous for HLA-D"H" (DB6) defined by the HTC, Herluf, and that the HLA-D typing results obtained by Herluf and SK are highly significantly correlated (Kendall's R = 0.46, p = 2.5 X 10(-5)). Both Herluf and SK are also homozygous for a new class II determinant, DN-1, defined by the monoclonal anti-B-lymphocyte antibody, 9w925, developed by Aizawa. The corresponding DN-1 antigen was present in 2.2% of 136 random, unrelated Danes and in all of six unrelated HLA-D"H" positive but in none of 20 HLA-D"H" negative individuals. Thus, there is an absolute and highly significant (p = 4 X 10(-6)) association between the cellularly defined HLA-D"H" determinant and the serologically defined DN-1 antigen, which strongly suggests that HLA-D"H" can now be detected serologically. DN-1 may be identical to DRw12 which is, however, poorly defined. The HTC-donor SK was immunized by pregnancy, and her serum contains anti-HLA-B7, which can easily be absorbed, and anti-B-lymphocyte antibodies which reacted with cells from 87.7% of 536 unrelated Danes. The reaction pattern of this serum is negatively associated with DR3, w6, and w8. This serum may define a new broad, cross-reacting antigen belonging to the same group as DRw52 and DRw53 or DQw1-w3, but it is clearly different from each of these antigens.