ASSOCIATIONS BETWEEN SINGLE NUCLEOTIDE POLYMORPHISMS IN CYTOKINE GENES AND COSTIMULATORY MOLECULE EXPRESSION

2.2
TITLE: ASSOCIATIONS BETWEEN SINGLE NUCLEOTIDE POLYMORPHISMS IN CYTOKINE GENES AND COSTIMULATORY MOLECULE EXPRESSION

Anne Hutchings,¹ Mark R. Benfield,² Judith M. Thomas.¹

¹Surgery, University of Alabama at Birmingham, Birmingham, AL; ²Pediatrics, University of Alabama at Birmingham, Birmingham

Considerable individual variation in cytokine protein production has been reported, related to DNA base changes known as single nucleotide polymorphisms (SNP), especially within the promoter regions of TNF&agr;, IL–10, IL–6, TGF&bgr; and IFN&ggr;. Also, associations are being uncovered between membrane–bound accessory molecules on peripheral blood cells and disease incidence. This study was performed to investigate whether an association might exist between cytokine gene SNPs and costimulatory molecule expression on immune cells.

Whole blood was obtained from 105 renal transplant patients, with informed consent. Cytokine protein production from peripheral blood cells was measured by ELISA, following in vitro stimulation, and cell surface marker expression was determined with flow cytometry. Following DNA extraction, cytokine SNPs were typed using ARMS–PCR.

Incubation of peripheral blood cells with IL–6 resulted in increased surface CD80 and CD86 expression, while IL–10 decreased CD80 expression. There was a clear correlation of the IL–6 G “high” allele with increased CD80 expression, and the IL–10 G “high” allele with decreased CD80 expression. Investigation of the combined IL–6/IL–10 genotypes demonstrated a step–like trend towards increased CD80 expression from patients with the IL–6 G “high”/IL–10 A “low” genotype, compared to expression from patients with the IL–6 GC “intermediate”/IL–10 G “high” genotype. Additionally, the IL–6 GC “intermediate”/IL–10 G “high” genotype was associated with significantly lower CD80 expression (p < 0.05) than the IL–6 G “high”/IL–10 A “low” genotype. These data raise the possibility that specific genotypes are associated with local cytokine regulation of cell surface costimulatory molecule expression that, in turn, may impact in vivo immune responses and disease incidence.