Genotypic variation and phenotypic characterization of granzyme B gene polymorphisms.
BACKGROUND
Granzyme B has been associated with allograft rejection in solid organ transplantation. Single nucleotide polymorphisms (SNPs) in the granzyme B gene might impact its expression. The aims of this study were (1) to establish the frequency of two granzyme B SNPs (A-295G; Q-55R) in pediatric heart transplant (PHTx) recipients and (2) to determine their phenotypic expression in healthy individuals.


METHODS
Three hundred ninety-six PHTx patients (245 white non-Hispanic, 49 black non-Hispanic, 82 Hispanics, and 20 others) and 52 healthy controls were screened for Q-55R and A-295G. For the control samples, we assessed the frequency of granzyme B positive cells by ELISPOT assay after mitogen stimulation.


RESULTS
Among the PHTx recipients, 57% percent of the population carried the Q/Q genotype, whereas 6% were R/R homozygotes. Seven of 49 (14%) black non-Hispanics were R/R homozygotes, whereas 13 of 245 (5%) of white non-Hispanics and 5 of 82 (6%) Hispanics carried the R/R genotype (P=0.02). The A allele frequency of granzyme B A-295G (49.6%) was similar to that of the G allele (50.4%). However, 80% of Black non-Hispanics were A allele carriers compared with 68% of White non-Hispanics (P<0.0001). After mitogen stimulation, the frequency of granzyme B positive cells was higher in the Q/Q homozygotes compared with R/R carriers (P=0.006), whereas a similar frequency of granzyme B positive cells was noticed among the genotypes of A-295G SNP.


CONCLUSIONS
These data indicate that 55 Q/Q genotype is associated with increased in vitro expression of granzyme B.
Girnita
Diana M
DM
Department of Pathology, Thomas E Starzl Transplant Institute, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Webber
Steven A
SA
Brooks
Maria M
MM
Ferrell
Robert
R
Girnita
Alin L
AL
Burckart
Gilbert J
GJ
Chinnock
Richard
R
Canter
Charles
C
Addonizio
Linda
L
Bernstein
Daniel
D
Kirklin
James K
JK
Naftel
David
D
Zeevi
Adriana
A
D002648:Child; D017931:DNA Primers; D005006:Ethnicity; D014644:Genetic Variation; D005838:Genotype; D006084:Graft Rejection / Q000201:enzymology; D053804:Granzymes / Q000235:genetics*; D016027:Heart Transplantation / Q000276:immunology* / Q000473:pathology; D006801:Humans; D010641:Phenotype; D011110:Polymorphism, Genetic; D020641:Polymorphism, Single Nucleotide; D044469:Racial Groups; D012016:Reference Values
D017931:DNA Primers; D053804:Granzymes