title: Knops blood group polymorphism and susceptibility to Mycobacterium tuberculosis infection.
abstract: BACKGROUND
  Complement receptor 1 (CR1) protein carries the Knops blood group antigens and is the receptor for the major ligand involved in Mycobacterium tuberculosis (Mtb) adhesion to macrophages. Erythrocyte CR1 binds immune complexes (ICs) formed during Mtb invasion, facilitating their clearance by the host immune system. The occurrence of specific Knops blood group genotypes among African populations was investigated to evaluate their impact on resistance or susceptibility to Mtb infection.
  
  
  METHODS
  The distribution of the Knops blood group genotypes (McC and Sl) was compared between tuberculosis (TB) patients with confirmed diagnosis of Mtb in isolates and negative controls. Conditional logistic regression was used to access the association between genotypes distribution and susceptibility to Mtb infection.
  
  
  RESULTS
  At the McC locus, individuals heterozygous (McC(a) /McC(b) ) were more resistant to Mtb infection (odds ratio [OR], 0.42; 95% confidence interval [CI], 0.22-0.81; p = 0.007). Although less significant, a similar effect was conferred by Sl1/Sl2 genotype (OR, 0.05; 95% CI, 0.28-0.9; p = 0.02). This protective effect was maintained among individuals presenting the McC(b) /Sl2 haplotype (OR, 0.25; 95% CI, 0.08-0.74; p = 0.008).
  
  
  CONCLUSIONS
  Acquisition of McC(b) and Sl2 alleles among African population is correlated with resistance to Mtb infection, adding this bacterium to the list of mechanisms underlying the selection of the Knops blood group polymorphism among these populations.
authors.affiliation: Scientific Support Services, LifeShare Blood Centers, Shreveport, Louisiana 71106, USA. ghislain.noumsi@lifeshare.org
authors.forename: Ghislain T
authors.initials: GT
authors.lastname: Noumsi
authors.forename: Anatole
authors.initials: A
authors.lastname: Tounkara
authors.forename: Hama
authors.initials: H
authors.lastname: Diallo
authors.forename: Katrina
authors.initials: K
authors.lastname: Billingsley
authors.forename: John J
authors.initials: JJ
authors.lastname: Moulds
authors.forename: Joann M
authors.initials: JM
authors.lastname: Moulds
mesh_terms: D001789:Blood Group Antigens / Q000235:genetics*; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D016015:Logistic Models; D011110:Polymorphism, Genetic; D017463:Receptors, Complement 3b / Q000235:genetics*; D014376:Tuberculosis / Q000235:genetics*
chemical_list: D001789:Blood Group Antigens; C509991:CR1 protein, human; D017463:Receptors, Complement 3b