Research Article Increased Serum Interleukin-9 Levels in Rheumatoid Arthritis and Systemic Lupus Erythematosus: Pathogenic Role or Just an Epiphenomenon? Andréa Tavares Dantas, 1,2 Claudia Diniz Lopes Marques, 2 Laurindo Ferreira da Rocha Junior, 1,2 Mariana Brayner Cavalcanti, 1 Sayonara Maria Calado Gonçalves, 1 Pablo Ramon Gualberto Cardoso, 1 Henrique de Ataide Mariz, 1,2 Moacyr Jesus Barreto de Melo Rego, 1 Angela Luzia Branco Pinto Duarte, 2 Ivan da Rocha Pitta, 1 and Maira Galdino da Rocha Pitta 1 1 Laborat´ orio de Imunomodulac ¸˜ ao e Novas Abordagens Terapˆ euticas (LINAT), N´ ucleo de Pesquisas em Inovac ¸˜ ao Terapˆ eutica Suely Galdino (Nupit SG), Universidade Federal de Pernambuco (UFPE), Avenida Professor Moraes Rego, s/n, 50670-901 Recife, PE, Brazil 2 Servic ¸o de Reumatologia, Hospital das Cl´ ınicas, UFPE, Avenida Professor Moraes Rego, s/n, 50670-901 Recife, PE, Brazil Correspondence should be addressed to Maira Galdino da Rocha Pitta; mgrpitta@gmail.com Received 20 February 2015; Revised 4 May 2015; Accepted 5 May 2015 Academic Editor: George Perry Copyright © 2015 Andr´ ea Tavares Dantas et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. he purpose of this paper was to evaluate the levels of IL-9 in patients with SLE and RA compared with controls and the association of IL-9 levels with clinical and laboratory parameters. IL-9 levels were assessed in 117 SLE patients, 67 RA patients, and 24 healthy controls by ELISA. Clinical and laboratory parameters were recorded. he IL-9 serum levels were signiicantly higher in RA patients (4,77 ± 3,618 pg/mL) and in SLE patients (12,26 ± 25,235 pg/mL) than in healthy individuals (1,22 ± 0,706 pg/mL) ( < 0, 001). In SLE patients, there were no statistically signiicant associations or correlations between the levels of IL-9 and SLEDAI or other clinical and laboratorial parameters, with the exception of disease time, which showed a statistically signiicant negative correlation with IL-9 levels ( = −0, 1948;  = 0, 0378). In RA patients, no association or statistically signiicant correlation was observed with disease duration, DAS28, HAQ, rheumatoid factor positivity, or erosions on radiography. hese data demonstrated increased serum levels of IL-9 in SLE and RA patients, but further studies are needed to clarify the precise role of this cytokine and its potential use as therapeutic target. 1. Introduction he imbalance between efector and regulatory cell popula- tions (Treg) is of critical importance in the pathogenesis of various autoimmune disorders. According to the current paradigm, the proinlammatory axis of h1 and h17 cells is counter balanced by the cell populations h2 cells and Treg [1]. Interleukin-9 (IL-9) is a member of the gamma-chain family of cytokines, irst described as a member of a growing number of cytokines that have crucial roles in the develop- ment, proliferation, survival, and diferentiation of multiple cell lineages of both the innate and adaptive immune systems [2]. IL-9 production was irst associated with the h2 phe- notype, and many of the preliminary functions of IL-9 were tested in models of h2-associated immunity. However, it is now known that, under speciic conditions, regulatory (Tregs), h1, and h17 subset of T cells also express IL-9. Recently, it has been shown that IL-9-producing CD4+ T cells may represent the T helper subset h9 cells. In vivo T cells produce IL-9 in both proinlammatory and anti- inlammatory environments [3]. Hindawi Publishing Corporation Disease Markers Volume 2015, Article ID 519638, 6 pages http://dx.doi.org/10.1155/2015/519638