A study of cytokine protein secretion, frequencies of cytokine expressing cells and IFN-G gene polymorphisms in normal individuals

Background. Cytokines are major regulators of immune responses, and there is evidence that they play a role in allograft rejection. Before embarking on a detailed study of pretransplant cytokine profiles in renal allograft recipients, we wished to investigate variations in cytokine protein secretion, numbers of cytokine expressing T cells, and cytokine gene polymorphisms in normal volunteers. Methods. Twenty normal healthy volunteers were studied. Cytokine protein secretion [interleukin- (IL) 2, IL-4, IL-10, and interferon- (IFN) γ] and numbers of cytokine expressing CD3 ⁺ T cells (IL-2, IL-4, IL-10, and IFN-γ) were quantified by means of enzyme-linked immunosorbent assay and two-color flow cytometry respectively. IFN-γ gene polymorphisms were determined by polymerase chain reaction and autoradiography. Results. Large interindividual variations in both the quantity of IL-2, IL-4, IL-10, and IFN-γ cytokine protein secreted and numbers of IL-2 and IFN-γ expressing T cells were demonstrated. However, numbers of IL-4 and IL-10 expressing cells were found to be below detectable limits by flow cytometry. In the case of IFN-γ, a bi-modal distribution was seen for the quantity of protein secreted. In addition, correlations were observed between IL-2 protein and frequency of IL-2 expressing T cells. However, no relationship was found between IFN-γ protein levels, numbers of IFN-γ expressing cells and IFN-γ gene polymorphisms. Conclusions. We have demonstrated large differences in both numbers of T helper 1 cytokine expressing cells and the quantity of T helper 1 and T helper 2 cytokine protein secreted between normal individuals. Although the amount of IL-2 protein secreted appeared to be determined by the frequency of IL-2 expressing cells, this was not the case for IFN-γ.