Acta haemat. 71: 310-315(1984) © 1984 S. Karger AG, Basel 0001 -5792/84/0715-0310 $ 2.75/0 Unusual Phenotype (Leu 7% OKT4+, OKMl+) Expressed by Cells from a Patient with an Abnormal Expansion of Granular Lymphocytes Isabella Quinti, L. Pacilli, V. Zoli, Giuliana De Sanctis, E. Mannella, G. Bonomo, A. De Laurenzi, F. Pandolfi Department of Allergy and Clinical Immunology, La Sapienza University of Rome; Department of Haematology, S. Camillo Hospital; Department of Clinical Medicine VI, La Sapienza University of Rome; the National Center of Blood Transfusion of CRI, Rome, Italy Key Words. Chronic lymphocytic leukemia ■ Granular lymphocytes • Lymphoproliferative disorders • Monoclonal antibodies • NK activity Abstract. We report the case of a 70-year-old female with a lymphocytosis which was casually detected during a routine examination. Immunological studies revealed the ex pansion of granular lymphocytes (GL) with the following, previously undescribed phenotype: Leu 7+, OKT3+, OKT4+, OKT8", OKM1+. These cells were tested for their functional activities and found to exert neither helper nor suppressor functions in in vit ro tests. Cytotoxic activities demonstrated a strong ADCC and a markedly reduced NK function. 1 year later the clinical course has remained good without any treatment and we suggest that this case should be classified as an abnormal expansion of GL, despite the OKT4 positivity of the cells. Our data point out the importance of a careful immunological study of cells from these rare patients and suggest the existence of a normal GL population expressing the OKT4 phenotype, which is possibly expanded in this patient. Introduction Chronic lymphocytic leukemia (CLL) is usually substained by the expansion of mature B cells and chronic proliferations of T lymphocytes are infrequent and he terogeneous. With the recent development of mono clonal antibodies against lymphocyte sub populations it has become clear that sever al subpopulations of mature lymphocytes exist, which may proliferate in chronic T lymphoproliferative diseases. Two major groups of patients with T-CLL may be roughly identified: (1) the first one is char acterized by an expansion of cells forming E rosettes and with the morphology of granular lymphocytes (GL), which are usually Leu 7+; (2) the second group is characterized by a proliferation of OKT4 Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 1/24/2019 6:18:56 AM