Due to differential expression of chemokine receptors, the Th1 and Th2 subsets of CD4+ T cells differ in their migratory responses to chemokines. cells. In contrast, only Th2 cells produced MIP-2. The possible biological relevance of these data was substantiated by the finding that in vivo-polarized Th1 cells, but not Th2 cells, produced MIP-1 and lymphotactin while in vivo-polarized Th2 cells secreted MIP-2. The above data demonstrate that Th1 and Th2 cells differ in their ability to produce chemokines, suggesting that Th1 and Th2 subsets differentially contribute to recruitment of cells into inflammatory foci. CD4+ Th cells can be classified into functionally distinct subsets based on the profiles of cytokines they produce (30). Th1 cells secrete interleukin-2 (IL-2), gamma interferon (IFN-), and lymphotoxin, which predominantly promote cell-mediated immune responses to intracellular pathogens, whereas Th2 cells produce cytokines such as IL-4, IL-5, IL-6, IL-9, IL-10, and IL-13, which are involved in humoral and allergic responses (1, 28). The experimental murine model of contamination is usually a well-characterized system to investigate the in vivo significance of polarized Th1-Th2 responses. In this model the Th1-dominated response leads to healing of the contamination in resistant mouse strains such as in C57BL/6 whereas the Th2 type of response leads to severe disease development in SIRT4 susceptible BALB/c mice (44). The differentiation of Th1 and Th2 cells from na?ve precursor CD4+ T cells is dependent on a combination of host genetic factors, the local cytokine milieu, and the type and dose of antigen encountered (32). Cytokines can either positively or negatively regulate the development of Th subsets. IL-12 and IFN- are thought to drive the polarization of na?ve T cells toward Th1 cells, whereas IL-4 and IL-13 are important for the induction of Th2 responses. Moreover, IL-4 and IL-10 inhibit the differentiation into Th1 cells, whereas IFN- acts as a suppressor of Th2 polarization (12, 41). Chemokines are key regulators in the recruitment of appropriate effector cells to sites of inflammation. There is evidence that Th subsets differ in their migratory response to chemokines (2, 13, 14, 19, 21, 28, 37, 42, 45) due to differential expression of chemokine receptors. Th1 cells preferentially express CC chemokine receptor 5 (CCR5), CCR7, and CXC chemokine receptor 3 (CXCR3) (3, 35, 37), while Th2 cells predominantly express CCR3, CCR4, and CCR8 (3, 36, 37, 48). However, ARRY-438162 manufacturer Th cells not only respond to chemotactic ARRY-438162 manufacturer factors but also release them, thus contributing to the composition of the cell infiltrates in inflammatory foci (4, 38, ARRY-438162 manufacturer 46, 47). Although differential expression of chemokines by Th1 versus Th2 cells has been exhibited, the chemokine repertoire of the distinct Th-cell populations has not been extensively and comprehensively examined. In previous work, either Th1 and Th2 cell lines (38, 39, 46) or Th cells differentiated in vitro (4, 8, 33, 47) were analyzed. In the present study, the chemokine production of Th-cell clones and Th cells differentiated both in vitro and in ARRY-438162 manufacturer vivo was investigated. The gene expression of murine chemokines was investigated by applying the RNase protection assay (RPA) with template sets developed in our laboratory (31). In addition to the in vitro studies, we extended our analyses to Th1 and Th2 cells that were polarized in vivo using the murine experimental contamination model. Using all three sources of Th cells, we show that Th1 and Th2 cells exhibit distinct chemokine secretion patterns with selective production of macrophage inflammatory protein 1 (MIP-1) and lymphotactin by Th1 cells and of MIP-2 by Th2 cells. MATERIALS AND METHODS Immunologic reagents. Anti-murine CD3 monoclonal antibody (MAb) was purified from hybridoma 145-2C11 (24) supernatant (SN). Recombinant murine (rm) lymphotactin, rabbit polyclonal immunoglobulin G (IgG) antibody (Ab) to ARRY-438162 manufacturer murine MIP-1, and biotinylated rabbit polyclonal IgG Ab to murine lymphotactin were obtained from R&D Systems (Wiesbaden, Germany). rm MIP-1, rm MIP-2, and biotinylated rabbit polyclonal IgG Abs to murine MIP-1 and to murine MIP-2 were purchased from PeproTech (Frankfurt, Germany). Rabbit polyclonal IgG Abs to murine lymphotactin and.