© 2004 Blackwell Publishing Ltd 45 Parasite Immunology , 2004, 26, 45–52 Blackwell Publishing, Ltd. ORIGINAL ARTICLE E. granulosus-specific human T-cell lines Echinococcus granulosus-specific T-cell lines derived from patients at various clinical stages of cystic echinococcosis R. RIGANÒ, 1 * B. BUTTARI, 1 * E. DE FALCO, 1 E. PROFUMO, 1 E. ORTONA, 1 P. MARGUTTI, 1 C. SCOTTÀ, 2 A. TEGGI 3 & A. SIRACUSANO 1 1 Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, 2 Department of Cellular and Developmental Biology, University of Rome ‘La Sapienza’, Rome, Italy and 3 Department of Infectious and Tropical Diseases, University of Rome ‘La Sapienza’, Rome, Italy SUMMARY To investigate the role of T lymphocytes in the immune response to Echinococcus granulosus, using sheep hydatid fluid (SHF) and antigen B (AgB), we generated T-cell lines from patients with active, transitional and inactive hydatid cysts. We established 16 T-cell lines, eight specific to SHF and eight specific to AgB. At surface phenotyping 88–98% of cells displayed the helper/inducer CD4 antigen. In all patients, at all clinical stages of hydatid cyst disease, T-cell stimulation with SHF and AgB invariably amplified a large number of almost identical Vβ subfamily fragments. Irrespective of antigen- specificity, the two cell lines from the patient with an inact- ive cyst had a Th1 profile, because they exclusively expressed and produced IFN-γ. Conversely, the T-cell lines derived from the seven patients with active and transitional hydatid cysts had mixed Th1/Th2 and Th0 clones. The functional character- istics of the 16 T-cell lines differed markedly in the various clinical stages of cystic echinococcosis, thus providing new in vitro evidence that Th1 lymphocytes contribute decisively to the inactive stage of hydatid disease, Th2 lymphocytes in the active and transitional stages. The parasite-specific T-cell lines, especially the two Th1 lines from the patient with an inactive cyst, may help identify Th1 protective epitopes on SHF and AgB. Keywords Echinococcus granulosus, immune response, T- cell lines, Th1/Th2 cytokines INTRODUCTION The control of Echinococcus granulosus infection is a complex task that engages humoral and cellular components of the immune system (1,2). Protective immunity against infection with an extracellular pathogen is considered an essentially cell- mediated event, dependent on the interaction of macrophages with T lymphocytes (3,4). Our group has already provided evidence in bulk cultures of peripheral blood mononuclear cells (PBMC) that parasite-derived substances regulate the host immune response by inducing protection (Th1 expansion) or susceptibility to disease (Th2 expansion) (5–7). To inves- tigate how the various T lymphocytes contribute to protect- ive immune responses against parasites, establishing specific T-cell lines in vitro is important, because available cell resources are limited and also because complex cellular interactions often make lymphoid-cell responses unreliable (8,9). In this study, designed to investigate the role of T lymphocytes in the immune response to E. granulosus, we generated T-cell lines from patients with active, transitional and inactive hydatid cysts. We analysed the generated T-cell lines for antigenic specificity, phenotype, clonal composition and cytokine expres- sion. To investigate the frequency of individual cytokine- producing cells and to enumerate cell types that express Th1- or Th2-type cytokines, or both (Th0 cells), we detected intracellular cytokine expression. We also analysed cytokine production in culture supernatants. As antigens for this study, we elected to use sheep hydatid cyst fluid (SHF) and purified antigen B (AgB) because they induce in vitro proliferative responses in patients with cystic echinococcosis (CE) (7). MATERIALS AND METHODS Blood samples Blood samples were obtained from eight patients with CE (seven had cysts in the liver, one had cysts in multiple sites) *Both authors contributed equally to this paper. Correspondence: Dr Alessandra Siracusano, Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy (e-mail: siracusano@iss.it). Accepted for publication: 8 April 2004