MLC (HLA-D) typing: a family study.

The genetics of five HLA-D specificities (Dw1, Dw2, Dw3, Dw4 and Dw6) have been assessed in 21 normal families with four or more children. The HLA-D traits, as defined by typing response against homozygous typing cells, normally behave as dominant characters. The data support the concept of allelic factors. The locial flaw in the basic algorithm of MLC typing (HLA-D typing), i.e. to draw positive conclusions from negative observations, has been amply reinforced in the following studies. Five assignments could not be verified genetically under the assumption of dominant traits. Homozygous lack of specific response genes is among the mechanisms proposed as a cause for the phenomenon which has not yet been fully explained. The estimated magnitude of the frequency of false assignments is approximately 10%.