J. ment. Defic. Res. (1978) 22, 179 179 T AND B LYPMHOCYTE SUBPOPULATIONS IN DOWN'S SYNDROME. A STUDY ON NON-INSTITUTIONALISED SUBJECTS C. FRANGESCHI and F. LICASTRO Institute of General Pathology, Faculty of Medicine, University of Bologna P. PAOLUCCI and M. MASI Department of Pediatrics, S. Orsola Hospital, University of Bologna S. CAVICCHI Institute of Genetics, Faculty of Natural and Biological Sciences, University of Bologna MARIA ZANNOTTI Institute of General Histology and Embriology, Faculty of Medicine, University of Bologna, Italy Several reports suggest that Down's syndrome (D.S.) may be considered an immunodeficiency. Many immunological defects have been reported in D.S. patients. These include: unusual stisceptibility to infections {Siegel, 1948; Donner, 1934; 0ster, Mikkelsen and Neilsen, 1964; Penrosr and Smith, 1966. 0stpr, Mikkelsen and Nielsen, 1975), alterations ofig levels (Stiehm and Fudcnberg, 1966; (ireene, Shenker and KareUtz, 1968; Dyggvc and Clausen, 1970; Rundle, Clothier and Suddel, 1971; Lopez, 1974; Lopez, Ochs, Thulinc, Davis andWedgood, 1975; Burgio, Ugazio, Nespoli, Marcioni, Bottelli and Pasquali, 1975; Bernard, Sitruk, Bernard and Mattei, 1976; Seger, W'ildfuer, BuchJngcr, Romen, Catty, Dybas, Haferkamp and Stroder, 1976; Seger, Buchinger and Stroder, 1977; Whittinghani, Sharma, Pitt and Maekay, 1977), depressed reactivity lo skin-test antigens in viva (Sutnick, London and Blumberg, 1971), decreased responsiveness to phytohacmagglutinin (Agarwall, Biumberg, Gerstiey, London, Sutnick and Loeb, 1970; Melinan. Younkin and Baker, 1970; Rigas, Elsasscr and Hecht, 1970; Burgio et al., 1975; Whiuingham et al., 1977; Seger et al., 1977), diminished percentage of E rosette-forming cells (Griffiths, Sylvester and Baylis, 1969; Burgio, Ugazio and Nespoli, 1974; Burgio et al., 1975), defective antibody response (Siegel, 1948; Mande, Desclaux, Soulairac and Beucher, 1952; Griffiths et al, 1969; Lopez et al., 1975), susceptibility to the persistence of Australia antigen (Blumberg, Gerstiey, Hungerford, London and Sutnick, 1967; Sutnick, London, CJcrstley, Cronlund and Blumberg, 1968; Blumberg, Gerstiey, Sutnick. Millman and London, 1970; Fialkow, Blumberg, London, Sutnick and Ahuline, 1971), presence of anti-thyroid anto-antibodies {Mellon, Pay and Green, 1963; Burgio, Severi, Rossoni and Vaccaro, 1965; Flalkow el al., 1971), impaired chemotaxis and bacterial killing capacity (Kretschmer, Lopez-O.-;ujia, Dela Rosa and Armendarcs, 1974; Khan. Evam, Glass, Shin and Almonte, 1975; Seger et aL, 1976), impaired in vitro production of leucocyte migration inhibitory factor by lymphocytes and decreased cyclic AMP levels in lymphocyte membranes (Levin, Schiesinger, Received 6th March, 1978