Acute cardiac transplant rejection is associated with low frequencies of interleukin-4 producing helper T-lymphocytes rather than with interleukin-4 promoter or splice variants

Interleukin-4 (IL-4) is a cytokine of the Th2 subtype. It is suggested that Th2 cytokines are involved in induction of tolerance towards the graft after organ transplantation. Therefore, we studied the association between the frequencies of IL-4 producing helper T lymphocytes (IL-4 HTL) and acute rejection in a panel of 31 cardiac transplant patients. It was also investigated whether these frequencies were influenced by: (1) a single nucleotide polymorphism (SNP) at position -590 in the promoter region of the IL-4 gene, which influences the production level of IL-4; and (2) the expression of an IL-4 splice variant (IL-4delta2), which inhibits the IL-4 receptor. Frequencies of IL-4 HTL were determined by limiting dilution analysis. Genotyping for the SNP was carried out by sequencing. The ratio of wild type versus IL-4delta2 mRNA was determined by quantitative RT-PCR of mRNA isolated from stimulated MNC of cardiac transplant patients. Frequencies of IL-4 HTL were significantly higher in patients who did not suffer from acute cardiac transplant rejection, than in patients that suffered from at least one rejection episode requiring treatment in the first year after heart transplantation. The genotype of the promoter SNP and the ratio between wild type/splice variant IL-4 mRNA did not influence the measured frequencies of IL-4 HTL or the presence of transplant rejection itself.