Immunology Letters 74 (2000) 239 – 244 Innate immune response mechanisms in non-insulin dependent diabetes mellitus patients assessed by flow cytoenzymology Luis Llorente a, *, Hortensia De La Fuente a , Yvonne Richaud-Patin a , Claudia Alvarado-De La Barrera a , Alejandro Diaz-Borjo ´n a , Alfredo Lo ´ pez-Ponce b , Israel Lerman-Garber b , Juan Jakez-Ocampo a a Department of Immunology and Rheumatology, Instituto Nacional de la Nutricio ´n Salador Zubira ´n, Vasco de Quiroga 15, Tlalpan. CP 14000, Me ´xico, D.F., Mexico b Department of Endocrinology, Instituto Nacional de la Nutricio ´n Salador Zubira ´n, Vasco de Quiroga 15, Tlalpan. CP 14000, Me ´xico, D.F., Mexico Received 19 June 2000; accepted 20 June 2000 Abstract It is well known that infections in patients with diabetes mellitus are more severe, although there is controversy for increased susceptibility to them. Non-specific immune response mechanisms could be related to defense and/or susceptibility to pathogens. The aim of this study was to investigate the activity of several enzymes involved in the primary host defense mechanisms in non-insulin dependent diabetes mellitus (NIDDM). Twenty NIDDM females with a mean HbA 1c level of 8.19% were included. No patient had clinical evidence of infection. As controls 20 healthy females were studied. The enzymes tested were dipeptidyl- peptidase I (DPP-I), cathepsin B and D, NADPH oxidase and superoxide dismutase (oxidative burst) and collagenase. Isolated leukocytes were incubated with the specific substrates in pyrogen free conditions. The intracellular enzyme activity was analyzed by flow cytometry. Collagenase enzymatic activity was similar in the three leukocyte subpopulations studied. Oxidative burst induction in monocytes was comparable between both groups. Enzyme activity of cathepsin B and D in all cell subsets, oxidative burst in PMN cells, and DPP-I in lymphocytes and monocytes from patients, was higher than those from healthy females (P 0.05). Overall, our findings demonstrate an enhanced functional status of several intracellular leukocyte enzymes in NIDDM. Furthermore, the increased oxidative burst induction and the consequent production of free radicals, may contribute to vascular complications. Other mechanisms — either from the non-specific or specific immune response — deserve investigation to establish if diabetic patients are more susceptible to infectious diseases. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Leukocytes; intracellular enzymes; diabetes; non-specific immune response; flow cytometry www.elsevier.com/locate/ 1. Introduction It is widely stated that in patients with diabetes mellitus infections are more severe [1]. The components of the innate immune system constitute the first line of defense against many microorganisms and have a key role in the control of bacterial infections. These func- tions are dominated by phagocytic cells, mainly neu- trophils and macrophages, able to kill invading microorganisms by releasing several components from granules (neutrophils) or lysosomes (macrophages) [2]. Another important mechanism involved in the elimina- tion of pathogens is the oxidative burst. Upon stimula- tion both macrophages and polymorphonuclear cells (PMN), markedly enhance their oxygen uptake leading to toxic metabolites for the infectious agents [2,3]. In diabetes mellitus patients the increased frequency of complicated soft-tissue, lower respiratory, and uri- nary tract infections, is due, at least in part, to de- ficient leukocyte functions [1]. Macrophages and PMN from these patients have shown impaired phago- cytosis as well as bactericidal activity [4 – 6]. Moreover, it has been reported derangements in other cells in- volved in specific immune response against infections * Corresponding author. Tel.: +52-56-555-954; fax: +52-55-732- 096. E-mail address: lllyrp@quetzal.innsz.mx (L. Llorente). 0165-2478/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S0165-2478(00)00255-8