JAL38 Antibody

Definition and Biological Context

The JAL antigen (ISBT symbol: RH48) is a rare blood group antigen predominantly found in individuals of Caucasian or African descent . Antibodies against JAL (anti-JAL) are clinically significant, as they can cause hemolytic disease of the fetus and newborn (HDFN) and transfusion reactions .

Serologic Characteristics

JAL+ red blood cells (RBCs) exhibit weakened expression of Rh antigens depending on haplotype:

• Key Findings:

  • Caucasian JAL+: Associated with the RHCE CeMA allele, leading to reduced C and e antigen expression .

  • Black JAL+: Linked to the RHCE ce S(340) allele, causing weakened c, e, V, and VS antigens .

  • Anti-JAL antibodies are often accompanied by alloanti-c, alloanti-e, or anti-CEST (an antibody targeting the high-prevalence antigen antithetical to JAL) .

Hemolytic Disease of the Newborn (HDFN)

Anti-JAL antibodies have been implicated in severe HDFN cases due to their ability to cross the placenta and target fetal RBCs .

Transfusion Challenges

• JAL+ RBCs may be misclassified during routine typing due to weakened antigen expression .

• Transfusion of JAL– blood to sensitized JAL+ patients can trigger hemolytic reactions .

Immunogenicity and Antibody Production

• JAL+ individuals may produce multiple alloantibodies (e.g., anti-c, anti-e) post-transfusion, complicating blood compatibility .

• Anti-CEST antibodies recognize the high-prevalence CEST antigen, which is absent in JAL+ individuals .

Genetic and Molecular Basis

• The JAL antigen arises from mutations in the RHCE gene, altering Rh protein conformation and antigen accessibility .

• Weakened antigen expression is attributed to steric hindrance or epitope masking caused by the JAL mutation .

Case Studies and Prevalence

• A Swiss study identified JAL in 0.06% of French-speaking donors, highlighting its rarity .

• Case reports describe JAL+ patients developing antibodies post-transfusion, necessitating antigen-negative blood .

Future Directions

• Genotyping: Critical for identifying JAL+ individuals in prenatal and transfusion settings.

• Antibody Monitoring: Essential for managing sensitized patients to prevent adverse outcomes.

This synthesis underscores the importance of recognizing JAL antigen variants and their associated antibodies in clinical practice. Further studies are needed to elucidate the structural basis of JAL’s immunogenicity and improve detection methods.