Comparative evaluation of 'TaqMan' RT-PCR and RT-PCR ELISA for immunological monitoring of renal transplant recipients

Quantitative detection of changes in cytokine gene expression in peripheral blood mononuclear cells correlates with and precedes acute rejection in renal transplant recipients

Immunological monitoring of transplant recipients is an attractive concept. Cytokines provide an obvious focus for research, as they are central to the human immune response. This study aimed to identify cytokines whose sequential gene expression differentiated rejectors from non-rejectors immediately following renal transplantation. Forty-five renal transplant recipients (15 rejectors) and 13 living donors were recruited. Total RNA was extracted from the peripheral blood mononuclear cells and reverse transcribed. Cytokine gene expression levels of IL-4, IL-10, TNF-alpha and TGF-beta1 were measured using TaqMan. IL-10 expression increased significantly following donor surgery. IL-4 and TNF-alpha patterns clearly differentiated between rejectors and non-rejectors. In the rejectors significant increases occurred more than 48 h before clinical graft dysfunction. Negative predictive values were 76% and 80% for IL-4 and TNF-alpha, respectively. This study has identified two cytokines (IL-4 and TNF-alpha) whose gene expression patterns differentiate between rejecting and non-rejecting renal transplant recipients making immunological monitoring possible.

House keeping genes and gene expression analysis in transplant recipients: a note of caution

BACKGROUND

House keeping genes are often used as a means of standardising results obtained in gene expression investigations. This study was performed to investigate whether beta-actin, beta2-microglobulin (two genes frequently quoted as house keeping genes) and/or transferrin receptor would be suitable house keeping genes for use in gene expression analysis of renal transplant recipients.

METHODS

Sequential expression of all three genes was measured in the peripheral blood mononuclear cells of 13 living donors and 45 renal transplant recipients, pre-operatively and then daily for up to 2 weeks. Fifteen of the recipients experienced an episode of biopsy proven acute rejection. Gene expression measurement was performed using quantitative real time 'TaqMan' PCR technology.

RESULTS

Gene expression of all three genes was unchanged in the living donor cohort. However, in the transplant recipients there were significant increases in expression following transplantation in the non-rejectors, and preceding the diagnosis of acute rejection. In the latter group, levels returned to pre-transplant values after the commencement of anti-rejection therapy.

CONCLUSIONS

Beta-actin, beta2-microglobulin and transferrin receptor gene expression, although not influenced by surgery, is influenced by transplantation, acute rejection and anti-rejection therapy making these genes unsuitable as house keeping genes following renal transplantation. These findings may cast doubt on the results of some studies that used these genes for the purposes of standardisation when looking at cDNA measurement. We suggest that any group wishing to use a house keeping gene ensure that its expression is independent of study parameters prior to the start of the study.