Intra HLA-D/DR region recombinant detected by primed lymphocyte typing (PLT)

Restriction fragment length polymorphism of the HLA-DP subregion and correlations to HLA-DP phenotypes

The restriction fragment length polymorphism (RFLP) of the class II HLA-DP subregion of the major histocompatibility complex (MHC) of humans has been unraveled by Southern blotting using DP alpha and DP beta probes in a study of 46 unrelated individuals with known HLA-DP types. Contrary to earlier preliminary findings with a limited number of enzymes, the RFLP appears to be quite extensive both with the DP beta (14 different DNA markers defined by individual fragments or clusters thereof) and the DP alpha (8 markers) probes, especially when enzymes recognizing only four base pairs were used. A few markers were absolutely or strongly associated with individual DP antigens, whereas most were associated with two or more DP antigens as defined by primed lymphocyte typing. Thus, Southern blotting seems feasible for typing for most DP determinants by specific fragments or subtraction between the various more broadly reactive DNA markers, and the RFLP provides further information on the DP subregion in addition to that provided by primed lymphocyte typing. In two recombinant families, the DP beta and DP alpha DNA markers segregated with DP antigens, whereas the DR beta, DQ beta, DQ alpha, and DX alpha markers followed the DR and DQ antigens.

The HLA-DP polymorphism in Denmark investigated by local and international PLT reagents. Definition of two "new" DP antigens

Lymphocytes from highly selected donors were primed for 10 days and subsequently bulk-expanded in IL 2 (TCGF) containing cultures. Two well-discriminatory PLT (CDP = Copenhagen DP) reagents against each of the DPw1-w6 specificities and one against each of the two "new" specificities, CDP4s and CDPHEI, were selected for further studies. Three combinations made in two recombinant families and four of ten HLA-A, B, and DR compatible combinations discriminated well in contrast to seven of 46 DR compatible, but HLA-A or B incompatible combinations. All reagents gave highly reproducible results, and high correlations (r-values between 0.73-1.00) for DP assignments were obtained with CDP and GNN reagents. No triplets were found for the DPw1-w6 and CDP HEI specificities. The "new" specificity CDP HEI defined in an HLA-DR/GLO recombinant family gave a coefficient of correlation with GNN 8 of 0.91. Another "new" specificity, CDP4s constitutes a subgroup ("split") of DPw4. The gene frequencies of DPw1-w6 estimated in 102 unrelated randomly selected Danes agreed with those reported for other Caucasoid populations. The gene frequencies CDP HEI and CDP4s were 0.03 and 0.08, respectively. The associations between DR3-DPw1, DR2-DPw4, and DRw6-DPw2 were confirmed. It is concluded that DP-typing with bulk-expanded reagents is a reliable and so far the only technique which can reveal the polymorphism of the DP gene products.

An HLA-DR/DP recombinant family involving DPw6. Evidence for cross-reactivity between DPw6 and GNN2B

HLA typing of an HLA-B/GLO recombinant family using bulk-expanded DP(SB) alloreactive T-cells (GNN1 to 6) as well as conventional HLA-ABC, D, DR, and DQ typing showed that a paternal recombination had taken place between HLA-DR and DQ on the one hand and HLA-DP(SB) on the other. The recombinant child was DPw4,6-heterozygous and differed in terms of class II determinants only for DPw6 from two otherwise HLA identical siblings, who were probably DPw4/4-homozygous. These siblings did not stimulate the recombinant in MLC whereas they responded to his cells indicating that DPw6 can stimulate in primary MLC. Moreover, it was possible to generate and bulk-expand DPw6-reactive lymphocytes (PLs) between MT and MA as responders and BN as stimulator. The correlation coefficient (r) between the reaction of these PLs and the GNN6 (anti-DPw6) reagents was 1.0 when tested against a panel of 71 individuals. This is the first report demonstrating that the DPw6 gene, like the DPw1-w5 genes, is located between DR/DQ and GLO. The frequency of the DPw6 antigen in 41 unrelated, randomly selected Danes was 7%. HLA-DP typing of the BN family revealed that the DPw6 positive but not DPw6 negative family members gave intermediate responses with one (GNN2B) but not with another (GNN2A) anti-DPw2-reagent. Studies of 63 healthy individuals (unrelated to the BN family) revealed seven similar discrepancies between GNN2A and GNN2B. Strikingly, all four DPw6 positive stimulators gave rise to such discrepancies indicating that the GNN2B reagent is cross-reactive and recognize a common part of the DPw2 and DPw6 molecules. No cases of GNN2A+/GNN2B- stimulators were found.

One-way positive cellular reactions between two HLA-A, B, C, D/DR genotypically identical brothers following active allogeneic immunization

The HLA-D/Dr region in man encodes major determinants which stimulate T lymphocytes to proliferation. The genetic organization of this region is apparently complex and is at present largely unknown. One obstacle is the scarcity and quality of available typing reagents. In an attempt to obtain high quality anti-DR sera, a series of active immunizations was performed between highly selected, healthy unrelated donors and recipients. One recipient (AR8) was immunized using cells incompatible for HLA-A2, B40 (w60), Cw3 and D/DRw6 and readily developed anti-A2 and B40 antibodies but no anti-C, CR, or other antibodies. When tested against his HLA genotypically fully identical brother using te cellular MLC, PLT, or CML techniques before immunization, results were mutually negative as expected. Following immunization, however, AR8 was able to mount MLC, PLT, and possibly CML responses against lymphocytes from the brother while the reverse combinations remained negative. When tested in the family the trait(s) thus identified seems to be maternally inherited. These results suggest the existence of minor histocompatibility determinants encoded from regions not closely linked to HLA. The brother of AR8 and the immunizing donor thus seem to share one or more determinants not possessed by AR8.