The Cromer blood group system: a review

Area of Science:

• Immunogenetics
• Hematology
• Complement System Biology

Background:

• The Cromer blood group system antigens are located on the decay accelerating factor (DAF) protein, a key regulator of complement activation.
• DAF is part of the regulators of complement activation (RCA) gene family and comprises four short consensus repeat (SCR) domains.
• The Cromer system includes eight high-incidence and three low-incidence antigens, with known molecular underpinnings in the DAF gene.

Purpose of the Study:

• To detail the molecular basis and clinical significance of Cromer blood group system antigens.
• To elucidate the role of DAF in red blood cell antigenicity and immune responses.
• To investigate the implications of Cromer antigen antibodies in transfusion medicine and pregnancy.

Main Methods:

• Analysis of single nucleotide polymorphisms (SNPs) within the DAF gene.
• Characterization of DAF protein structure and function.
• Review of clinical cases involving anti-Cromer antibodies and transfusion outcomes.

Main Results:

• Most Cromer antigens result from SNPs in the DAF gene, mapping to SCR regions.
• The Inab phenotype represents a complete DAF deficiency on red blood cells (RBCs).
• Anti-Cromer antibodies are infrequent but can lead to accelerated destruction of transfused RBCs.

Conclusions:

• The molecular genetics of Cromer antigens are well-defined, linked to DAF variations.
• While anti-Cromer antibodies pose a transfusion risk, hemolytic disease of the newborn is unlikely due to placental DAF.
• Understanding DAF's role is crucial for managing blood transfusion compatibility and pregnancy in individuals with Cromer system variations.