112-P: HLA-DR53 NULL (DRB4∗03:01N) ALLELE IN TWO UNRELATED INDIVIDUALS

Aim To describe two subjects carrying HLA-DRB4 ∗ 03:01N allele. Methods Molecular typings were done with LabType SSO (One lambda) and SSP (Olerup) kits. Results Two unrelated individuals for living donor renal transplant workup were typed with rSSOP method ( Table 1 ). The absence of DR7-associated DR53 was intriguing. Tests with DRB4 ∗ SSP revealed the presence of DRB4 ∗ 03:01N allele in both subjects. HLA-DRB4 ∗ 03:01N is a null allele found in haplotype of DQB1 ∗ 07:01-DQA1 ∗ 02:01-DQB1 ∗ 02:02 (Robbins, F., Immunogenetics (1997) 46: 104–110). There is a deletion of exon 2 for DRB4 ∗ gene so DR53 will not be expressed. The rSSOP DRB3/4/5 ∗ typing kit from One lambda only can detect polymorphisms on exon 2 of HLA-DRB4 ∗ . Although DRB4 ∗ 03:01N is not amplified in rSSOP, the positive control bead for exon 2 is still positive if the 2nd DRB3/4/5 ∗ antigen is present. The haplotype A ∗ 32:01-B44:03-C ∗ 16:01-DRB1 ∗ 07:01-DRB4 ∗ 03:01N- DQA1 ∗ 02:01-DQB1 ∗ 02:02 was clearly deduced in family haplotype studies on subject #2. This haplotype is also found in unrelated subject #1. Large studies may need to done to determine the frequency of HLA-DRB4 ∗ 03:01N allele and whether DRB4 ∗ 03:01N is often associated the haplotype or not. Conclusions Extra typing to determine the presence of HLA-DRB4 ∗ 03:01N can be done when there is A ∗ 32:01-B44:03-C ∗ 16:01-DRB1 ∗ 07:01-DQB1 ∗ 02:02 haplotype. Defining this DR53 null allele in organ donors will be helpful to ensure patients with anti-DR53 antibodies will not be excluded in virtual crossmatch for donors carrying DR7-DQ2 haplotype. This is also helpful for unrelated hematopoietic stem cell transplant.