Diabetologia (1996) 39:60-69 Diabetologia 9Springer-Verlag 1996 Elevated serum levels of macrophage-derived cytokines precede and accompany the onset of IDDM M. J. Hussain 1 , M. Peakman 1 , H. Gallati 5, S. S. S. Lo 4 , M. aawa 4, G. C. Viberti 3, P. J. Watkins 2, R. D. G. Leslie 4, D. Vergani 1 1Department of Immunology, King's College School of Medicine and Dentistry, London, UK 2Department of Medicine and Diabetes, King's College School of Medicine and Dentistry, London, UK 3Unit for Metabolic Medicine, United Medical and Dental Schools, Guy's Hospital, London, UK 4Department of Diabetes, St Bartholomew's Hospital, London, UK 5E Hoffmann-La Roche, Basel, Switzerland Summary To determine whether cytokines could have a role in the development of insulin-dependent diabetes mellitus (IDDM), we measured serum levels of cytokines derived from T helper i (interleukin-2 and interferon- 7), T helper 2 (interleukin-4 and inter- leukin-10) lymphocytes and macrophages (tumour necrosis factor-a, interleukin-1 a and interleukin- 1/3) in patients before and after the onset of IDDM. Recently diagnosed IDDM patients had significantly higher levels of interleukin-2, interferon-y, tumour necrosis factor-a and interleukin-1 a than patients with either long-standing IDDM, non-insulin-depen- dent diabetes (NIDDM), Graves' disease, or control subjects (p < 0.05 for all). Compared with control subjects, patients with long-standing IDDM and those with NIDDM had higher interleukin-2 and tu- mour necrosis factor-a levels (p < 0.01 for all). Inter- leukin-4 and interleukin-10 were detectable in sera of patients with Graves' disease only, while interleu- kin-1/3 was not detectable in the serum of any control or test subject. To investigate whether high cytokine levels precede the onset of IDDM, we studied 28 non-diabetic identical co-twins of patients with IDDM, followed-up prospectively for up to 6 years after the diagnosis of the index. Levels of tumour ne- crosis factor-a and interleukin-1 a were elevated above the normal range more frequently in the eight twins who developed diabetes than in those 20 who did not (p < 0.005). Anatysis of T helper i and T help- er 2 profiles of the twin groups did not reveal a clear difference between prediabetic twins and twins re- maining non-diabetic. These results support the no- tion that T helper i lymphocytes may play a role in the development of IDDM. This is associated with re- lease of macrophage-derived cytokines, which is also a feature of the prediabetic period. The lack of evi- dence of a dominant T helper 1 profile of cytokine re- lease before diabetes onset suggests that additional events, activating this arm of the cellular immune re- sponse, are required in the immediate prediabetic pe- riod. [Diabetologia (1996) 39: 60-69] Key words Cytokines, T helper subsets, interleukin-2, interferon-y, inter!eukin-1, tumour necrosis factor, prediabetes, identical twins. Received: 15 March 1995 and in revised form: 29 May 1995 Corresponding author." Professor D.Vergani, Department of Immunology, King's College School of Medicine and Den- tistry, Bessemer Road, London SE5 9PJ, UK Abbreviations: IL, Interleukin; IFN-v, interferon-gamma; TH, T helper; ICA, islet-cell antibody; GAD, glutamic acid decar- boxylase; IDDM, insulin-dependent diabetes mellitus; NIDDM, non-insulin-dependent diabetes mellitus; TNF-cq tu- mour necrosis factor-alpha; CTLL-16, murine cytotoxic cell line. There is evidence to suggest that T lymphocytes and macrophages play a crucial role in mediating beta- cell damage and causing insulin-dependent diabetes mellitus (IDDM) [1-6]. A mononuclear cell infil- trate, which includes T lymphocytes and macro- phages, is a characteristic feature of the islets of Langerhans at diagnosis [2-5]. T lymphocytes could be directly responsible for beta-cell damage, or they could provoke injury through recruitment of macro- phages. Macrophages are the first cells to appear in considerable number during insulitis in animal mod- els of diabetes [6]. Both activated T cells and macro-