Identification of the DRB4*01:03:01:02N null allele with HLA-DRB1*04 in a Spanish donor.

The association between the DRB4*01:03:01:02N null allele and the HLA-DRB1*07~DQB1*03:03 haplotype has often been reported. Nevertheless, more unusual associations have also been found in other countries, such as its association with HLA-DRB1*04. HLA class I and II antigen typing is currently performed using DNA-based methods, making it more difficult to identify null alleles than if serological methods were used. Furthermore, the DRB3/4/5 loci are not usually studied. However, the identification of non-expressed HLA alleles is of great importance for transplantation so it is necessary to identify HLA antigen associations with null alleles and report these findings. In this paper, we describe the association of DRB4*01:03:01:02N null allele with DRB1*04 for the first time in Spain.