Jk_null alleles in two patients with anti-Jk3

As of publication, a total of 41 null alleles have been acknowledged by the International Society of Blood Transfusion (ISBT) to cause the rare Jk_null phenotype, but none have been discovered in Austria thus far.

Two patients with anti-Jk3 were serologically identified by a positive antibody screening and typed as Jk(a-b-). The initial genotyping using an SSP-PCR method for the common 838A/G polymorphism indicated a JK*02/02, or JK*01/02 genotype, respectively. To find the disruptive mutations, Sanger sequencing was performed and results were compared to the reference sequence. The patient's antibodies were characterized with a monocyte monolayer assay (MMA) for their potential clinical significance.

Three novel null-mutations of the SLC14A1 gene were found in two patients. Patient 1 was homozygous for a 10bp deletion in exon 4 (c.157_166del on JK*02). Testing of her family members revealed Mendelian inheritance of the deletional allele. The other patient was compound heterozygous for two mutations: one allele carrying a single base deletion in exon 4 (c.267delC on JK*01) and the other a splice site mutation in intron 3 (c.152-1g>a on JK*02). The MMA results suggest high clinical significance of the anti-Jk3 in both patients.

The detected mutations led to Jk_null phenotypes and are the first description of JK_null alleles in the Austrian population.