CLINICAL IMMUNOLOGY AND IMMUNOPATHOLOGY 50, 146-153 (1989) BRIEF COMMUNICATION Increased Levels of Soluble CD8 Molecule in the Serum of Patients with Acquired lmmunodeficiency Syndrome (AIDS) and AIDS-Related Disorders C. AGOSTINI, G. SEMENZATO,’ F. VINANTE, A. SINICCO, L. TRENTIN, R. ZAMBELLO, B. ZUPPINI, R. ZANOTTI, F. SIVIERO, D. VENERI, R. FoA, AND G. PIZZOLO Department of Clinical Medicine, First Medical Clinic and Clinical Immunology Branch, Padua University; Department of Hematology, Verona University; Institute of Infectious Disease, Torino University; Department of Clinical Pathology, Cittadella Hospital, Padua; and Department of Biomedical Sciences and Human Oncology, Medical Clinic Section, Torino University, Italy In this study we investigated the serological levels of the soluble form of the CD8 molecule (s-CDS) in 97 human immunodeficiency virus (HIV) seropositive patients. The control groups included 20 normal heterosexual subjects and 19 healthy seronegative subjects belonging to risk groups for AIDS. Our results show that patients with HIV infection have significantly higher levels of s-CD8 U/ml than the control groups. When the patients were further subdivided according to the Centers for Disease Control (CDC) classification, s-CD8 U/ml values were consistently increased in all HIV patients, irre- spective of the CDC stages. No statistically significant correlation was found between the serological levels of s-CDS/ml and the absolute numbers of CD8 lymphocytes/mm3, in both HIV seropositive patients and control groups. Since in the more advanced stages of HIV infection (IV-A, IV-Cl) the decrease in the absolute number of CDS’ cells was not followed by a decrease in s-CD8 levels, it is conceivable that an increased release and/or shedding of s-CD8 per cell might occur in these patients. In fact, when the results were expressed as s-CD8 units per CD8 positive cell (s-CD%absolute number of CD8), the levels of s-CDS/cell were higher in patients belonging to the IV-A and IV-Cl CDC groups (1.94 U/cell * 0.33 and 3.39 U/cell 2 0.5, respectively) compared to normal controls (P < 0.001). HIV seronegative subjects at risk for AIDS (P < O.OOI), and the other patients’ groups (II and III CDC groups, respectively, P < 0.001 and P < 0.001). The evidence herein provided that in patients with HIV infection s-CD8 levels are in- creased suggests a possible pathogenetic role of the cells involved in the release of this molecule. 8 1989 Academic Press. Inc. INTRODUCTION It is well established that the progressive depletion of peripheral blood CD4 lymphocytes is the hallmark of the acquired immunodeficiency syndrome (AIDS) (1). Recently, several reports have pointed out that the increase of circulating CD8 lymphocytes represents an additional consistent finding in patients at certain stages of human immunodeficiency virus (HIV) infection (24). In particular, it ’ To whom correspondence should be addressed at Istituto di Medicina Clinica, Clinica Medica I, via Giustiniani 2, 35128, Padova, Italy. 146 OO!%-1229/89 $1.50 Copyright 0 1989 by Academic Press, Inc. AII rights of reproduction in any form reserved.