Partial C antigen in sickle cell disease patients: clinical relevance and prevention of alloimmunization.
BACKGROUND
Partial Rh antigens have been widely described in black individuals. Carriers are prone to immunization when exposed to the normal antigens. In sickle cell disease (SCD), patient alloimmunization is a major cause of transfusion failure. The potential of individuals with partial C antigen to make anti-C has not been investigated. We sought partial C status and anti-C production in a cohort of SCD patients with the C+ phenotype, to determine whether exposure to normal C antigen should be avoided.


METHODS
We constituted a cohort of 177 randomly selected SCD patients expressing C antigen. We screened for (C)ce(s) and R(N) haplotypes, presumably associated with partial C antigen in Afro-Caribbeans, and we recorded the number of transfused C+ red blood cell (RBC) units, immunization status, and extended phenotype.


RESULTS
Forty-nine patients carried abnormal C antigen, deduced from the presence of (C)ce(s) and/or R(N), not compensated by a normal RHC allele in trans. Among patients with partial C phenotype exposed repeatedly to C+ RBCs, 30% produced anti-C. Two patients experienced hemolysis. In our hospital, with 22% of SCD patients expressing C, prevention of anti-C immunization for all individuals with partial C antigen would require a 7% increase in the use of C- RBC units. These RBCs are already in short supply for SCD patients who are C-.


CONCLUSIONS
This study demonstrates the need to detect partial C within C+ SCD patients and to prevent immunization. A larger number of Afro-Caribbeans donors is needed to provide these patients with C- RBCs.
Etablissement Français du Sang, Ile de France, Institut Mondor de Médecine Moléculaire, IM3, Unité des Maladies Génétiques du Globule Rouge, Hôpital Henri Mondor, Créteil, France.
Christophe
C
Tournamille
Natacha
N
Meunier-Costes
Bruno
B
Costes
Jennifer
J
Martret
Aurélie
A
Barrault
Philippe
P
Gauthier
Frédéric
F
Galactéros
Ruben
R
Nzouékou
Philippe
P
Bierling
France
F
Noizat-Pirenne
D000349:Africa / Q000208:ethnology; D000755:Anemia, Sickle Cell / Q000208:ethnology / Q000235:genetics / Q000276:immunology*; D001787:Blood Group Incompatibility / Q000276:immunology; D005602:France; D006239:Haplotypes; D006801:Humans; D007518:Isoantibodies / Q000097:blood*; D012189:Retrospective Studies; D012204:Rh-Hr Blood-Group System / Q000235:genetics / Q000276:immunology*; D065227:Transfusion Reaction; D014900:West Indies / Q000208:ethnology
D007518:Isoantibodies; D012204:Rh-Hr Blood-Group System