CELLULAR IMMUNOLOGY 139,9 1-97 (1992) Defect of CD2- and CD&Mediated Activation Pathways in T Cells of Atopic Patients: Role of lnterleukin 2 MARIA FIAMMETTA ROMANO,*,' GIULIANA VALERIo,Jf MARIA CATERINATURCO,$GIUSEPPE SPADARO,~ SALVATOREVENLJTA,$ANDSALVATOREFORMISANO* *Dipartimento di Biologia e Patologia Cellulare e Molecolare, TDipartimento di Pediatria, SDipartimento di Biochimica e Biotecnologie Mediche, and SCattedra di Immunologia Clinica e Allergologia, II Facoltd di Medicina e Chirurgia, Napoli, Italy Received May 1, 1991; accepted July 25, 1991 In the present work we analyzed the proliferative response of T lymphocytes from 11 atopic patients stimulated in vitro via either the CD2 or the CD3 pathway of cell activation. In both caseswe found a significant decrease of thymidine incorporation in cell DNA in comparison with T cells from normal donors. The mechanism of this impaired proliferative response was analyzed. Atopic patients’ T cells were found to secrete low quantities of interleukin 2 (IL2) and to express low amounts of Tat antigen, measured as both a percentage of Tac-positive cells and a mean fluorescence intensity of Tat antigen per cell. Addition of recombinant IL2 to cultures completely restored both cell proliferative response and Tat antigen expression. This effect was specific of IL2 since addition of IL1 or IL4 did not significantly affect T cell proliferative response. We conclude that atopic patients’ T lymphocytes have a defect in both CD2 and CD3 pathways of cell activation relying on impairment of IL2 production, without involving IL2 responsiveness or other lymphokine defects. Q 1992 Academic PWSS, Inc. INTRODUCTION A body of evidence suggests that atopy, the familiar allergic disorder involving an immediate type hypersensitivity to environmental allergens, is related to an impairment of T lymphocyte reactivity. Indeed, a decreased T cell proliferative response to bacterial antigens and/or an altered production of some T lymphocyte-derived cytokines in atopic patients has been reported by some authors (l-6). On the other hand, impair- ment of T cell reactivity in some clinical conditions (Nezelofs syndrome, Wiskott- Aldrich syndrome, GVDH, Hodgkin’s disease) is often accompanied by developing of symptoms of atopy (7-9). T lymphocyte activation is mediated by two different pathways involving antigen receptor (Ti-CD3) or CD2 molecule. Triggering of one of these structures induces T cell transition from Go to Gr phase and production and response to interleukins 2 and 4: these in turn regulate Gr progression and entry in S phase (10). In this paper ’ To whom correspondence should be addressed at Dipartimento di Biologia e Patologia Cellulare e Molecolare (Servizio di Immunoematologia e Trasfusione), II Facolti di Medicina e Chirurgia, Via S. Pansini, S-80 13 1 Napoli, Italy. Fax: 39-8 l-209224. 91 0008-8749192 $3.00 Copyright 0 1992 by Academic Press, Inc. All rights of reproduction in any form reserved.