Cytokine Gene Profile in Circulating Blood Mononuclear Cells from Patients with Systemic Lupus Erythematosus: Increased Interleukin-2 but not Interleukin-4 mRNA

Abstract

Cytokines are important in developmental and effector pathways of lymphocyte function. Our objective was to elucidate the profile of cytokines produced by circulating mononuclear cells from patients with systemic lupus erythematosus as estimated from studies of cytokine gene activation. cDNA prepared by reverse transcription of lymphocyte mRNA was amplified using the polymerase chain reaction and normalized on the basis of β-actin gene expression. Of 10 cytokines investigated in 16 individuals, differences between SLE and controls were found in only three. IL-2 transcripts were detected in four of six cases of subjects hospitalized for active SLE, but in only one of seven healthy controls, and none of three cases with pulmonary tuberculosis. By contrast, IL-4 transcripts were decreased compared with healthy controls and patients with tuberculosis. Also, TGFβ transcripts appeared to be decreased in SLE. All individuals studied regularly demonstrated high levels of transcripts for IL-1 beta, IL-6 and TNF alpha and transcripts for IFNy, TNFβ, IL-5 and IL-10 were variably expressed. In a second group of six SLE patients with less active disease, there was also a decrease in IL-4 expression compared with six healthy controls. Moreover, assays performed on sera from patients with active SLE revealed that IL-4 levels were not increased. Although in mice this cytokine has a well documented role in supporting antibody production, this study provides no evidence that IL-4 is involved in the B cell hyperactivity characteristic of human SLE.