Lack of the multidrug transporter MRP4/ABCC4 defines the PEL-negative blood group and impairs platelet aggregation.

The rare PEL-negative phenotype is one of the last blood groups with an unknown genetic basis. By combining whole-exome sequencing and comparative global proteomic investigations, we found a large deletion in the ABCC4/MRP4 gene encoding an ATP-binding cassette (ABC) transporter in PEL-negative individuals. The loss of PEL expression on ABCC4-CRISPR-Cas9 K562 cells and its overexpression in ABCC4-transfected cells provided evidence that ABCC4 is the gene underlying the PEL blood group antigen.

A LU:-16 individual with antibodies.

Antibodies against Lutheran blood group antigens have been observed during first-time pregnancy. Samples from a woman of African descent were tested in our immunohematology laboratory on several occasions since 2001. Her samples were phenotyped as Lu(a+b-), and anti-Lub was suspected but not identified.

Weak D type 42 cases found in individuals of European descent.

Patient samples were referred to our immunohematology reference laboratory to investigate the presence of a weak D antigen. In the last 3 years, 26 samples were received. Serology and molecular analyses were performed to identify the weak D variant.