Heterogeneity of HLA defined in PLT: a cellular assay detects differences not seen using HLA-DRw serology.

The primed lymphocyte typing test (PLT) is used to detect the gene products of the HLA-D region which are responsible for secondary restimulation of cells primed in MLC. Alternatively, products of the HLA-D region may be detected serologically using antisera directed against a subpopulation of lymphocytes; these are the so-called DRw determinants. The PLT was used to see if it were possible to detect heterogeneity within a given serologically defined group using a cellular test. As priming combinations, we used family members identical for one haplotype and differing in the HLA-A, B and C regions, but not the D region of the second haplotype. Our results indicated that it was possible to prime against this second haplotype and that the segregation of the difference followed HLA. Therefore, using a cellular test it was possible to detect differences among cells belonging to a given DRw group. This suggests that PLT can be a useful tool to identify those serological groups which are composed of heterogenous determinants. In addition, it points out the problem in using any one test to establish identity of the HLA-D region, especially for clinical purposes.