Endogenous IL-4 and IFN- are Essential for Expression of Th2, but not Th1 Cytokine Message During the Early Differentiation of Human CD4 T Helper Cells Karen C. L. Torres, Walderez O. Dutra, and Kenneth J. Gollob ABSTRACT: CD4 + T cells can be divided into several distinct effector subpopulations, including Th1 and Th2. Human Th1 cells are essential for the establishment of cellular immune responses, whereas Th2 cells for immu- noglobulin E synthesize by B cells and immunoregula- tion. This study determines the involvement of exog- enously and endogenously produced T cell– derived cytokines during early differentiation of naive CD4 + T cells into Th1 and Th2 cells. Cytokine gene expression of purified experienced and naive CD4 + T cells in the pres- ence or absence of Th-directing cytokines and neutralizing anti– cytokine antibodies, was determined at early (20 and 40 h) time points, after in vitro activation. These studies demonstrated that: (1) endogenously produced, T cell– derived cytokines (interferon [IFN]- and interleukin [IL]-4), play an important role in the regulation of early gene expression of Th2, but not Th1 type cytokines; (2) Th1-related cytokines, IFN-, and IL-2, are preferentially expressed in cultures directed toward Th1, as compared with Th2; and (3) IL-4 and IFN- showed early message expression in both differentiating populations, indicating a mixed profile of Th1 and Th2 cytokine production in early human Th cell development. These findings point to the critical role for endogenously produced cytokines in the early differentiation of human Th1 or Th2 cells. Human Immunology 65, 1328 –1335 (2004). © American Society for Histocompatibility and Immunogenetics, 2004. Published by Elsevier Inc. KEYWORDS: Th1; Th2; differentiation; gene transcrip- tion; cytokine ABBREVIATIONS B21 human Th0 cell line CY cychrome DTH delayed type hypersensitive FACS fluorescent-activated cell sorter mAbs monoclonal antibodies PE phycoerythrin PMBC peripheral mononuclear blood cells RT-PCR reverse transcriptase-polymerase chain reaction ThE CD4 + experienced T cells ThP naive CD4 + T cells INTRODUCTION Effector CD4 + T cells play an important role in the establishment of, or protection from, many diseases [1]. Distinct subsets of CD4 + T cells have been identified in experimental models and in humans, based on their cytokine profiles [2– 4]. In particular, the subsets Th1 and Th2 display key effector functions and immunoregu- latory properties, determining the outcome of immune responses. Th1 effector cells secrete interferon (IFN)-, interleukin (IL)-2, and tumor necrosis factor (TNF)-, and are involved in activation of monocytes, induction of delayed type hypersensitive (DTH) response, and cause inflammation with tissue damage [5–7]. Th2 effector cells secrete mainly IL-4, IL-5, and IL-13 and are gen- erally involved with immunoregulation, induction of From the Departments of Biochemistry-Immunology (K.C.L.T., K.J.G.) and Morphology (W.O.D.), Belo Horizonte, Brazil. Address reprint requests to: Kenneth J. Gollob, Ph.D., UFMG-ICB, Department of Biochemistry-Immunology, Av. Antonio Carlos, 6627, C.P. 486, Belo Horizonte, MG 30161-970, Brazil; Tel/Fax: 55-31-3499- 2655; E-mail: kjgollob@mono.icb.ufmg.br. Received February 5, 2004; revised June 11, 2004; accepted June 15, 2004. Human Immunology 65, 1328 –1335 (2004) © American Society for Histocompatibility and Immunogenetics, 2004 0198-8859/04/$–see front matter Published by Elsevier Inc. doi:10.1016/j.humimm.2004.06.007