HLA-DRB1 alleles and Jk(a) immunization.

Background: In transfusion medicine, anti-Jk(a) has been implicated in hemolytic transfusion reactions. Development of anti-Jk(a) after transfusion does not always occur after Jk(a-) patients receive at least 1 unit of Jk(a+) blood unit. This study was designed to identify HLA-DRB1 alleles associated with predisposition to Jk(a) immunization after blood transfusion or pregnancy.

Study Design And Methods: Genotyping by polymerase chain reaction and sequence-specific oligonucleotide probe nonradioactive hybridization/sequence-specific primers was performed in 20 Jk(a)-immunized patients and 200 controls from the same southern European population.

Results: Genotyping showed that HLA-DRB1*01 was significantly more frequent in Jk(a)-immunized patients than controls: 55 percent versus 17 percent (odds ratio [OR], 5.9; confidence interval [CI], 2.3-15.5; corrected p value<0.05). Because HLA-DRB1*0101, DRB1*0102, and DRB1*1001 share a common sequence in their B1 chain, that is, F in 13, R in 71, and A in 74, HLA genetic predisposition was analyzed by comparing patients and controls with respect to the distribution of F13/R71/A74-positive and -negative alleles. Results demonstrated greater positivity of the F13/R71/A74 sequence (DRB1*0101, *0102, or *1001) in patients than in controls: 65 percent versus 19.5 percent (OR, 7.7; CI, 2.9-20.5; p<0.001).

Conclusion: In conclusion, HLA-DRB1*0101, DRB1*0102, and DRB1*1001, which share a common DRB1 sequence, appeared to be overrepresented in Jk(a)-immunized patients.