Original research article/Artykul oryginalny Leukotrienes deficiency Gabriela Turek, Rafal Pawliczak * Department of Immunopathology, Chair of Allergology, Immunology and Dermatology, Faculty of Medical Science and Postgraduate Training, Medical University of Lodz, Poland Introduction Leukotrienes (LTs) are products of 5-lipoxygenase (5-LO) action. They are known as potent mediators of inflammation in the upper and lower airways. Leukotrienes are divided into two groups: LTB 4 and cysteinyl-LTs (LTC 4 , LTD 4 , LTE 4 ) [1]. They were first described in the period 1938 and 1940 when Feldberg and Kellaway identified a ‘‘slow reaction smooth muscle-stimulating substance’’ (SRS), which was later named LTC 4 [2]. SRS was first identified as a result of cobra venom administration to guinea-pig lungs. The main problem was isolating the effects of the venom from those of histamine, which was made possible only after anti-histamine drugs were invented. Blocklehurst, using anti-histamine drugs, described the formation of SRS-A in anaphylaxis in 1960 [3], Drazen and Nicosia emphasized the important role of SRS-A in asthma in the 1980s, while Samuelsson discovered that SRS-A is a mixture of cysteinyl-LTs [4–6]. In 1981 Dahlen et al. confirmed that leukotrienes induce microcir- culatory alterations similar to those seen in the early phases of acute inflammatory response [7]. Leukotriene B4 has been known as a chemoattractant for phagocytes since 1983 [4]. 5-LO and LTs 5-LO, after activation by FLAP, synthesizes 5-HPETE from arachidonic acid (AA) in response to inflammatory and immune stimulation. 5-HPETE is then quickly transformed to leukotriene A 4 (LTA 4 ). LTA 4 is the first of the generated leukotrienes and acts as a substrate for LTA 4 hydrolase or LTC 4 synthase. The molecular mechanism of transferring LTA 4 to LTC 4 involves glutathione, while H 2 O is needed for its conversion to LTB 4 . LTC 4 is converted to LTD 4 and LTE 4 (Fig. 1) [8]. alergologia polska- polish journal of allergology 1 (2014) 19–26 article info Article history: Received: 03.01.2014 Accepted: 11.02.2014 Keywords:  Leukotriene  Patology  Human abstract There are many diseases connected with deficiency of leukotrienes, but all people suffe- ring from this are also exposed to infection. This is a result of low amounts of cysLTs and LTB 4 , which are potent inflammatory mediators, resulting in the host defenses of people with decreased levels of leukotrienes being impaired. Bacteria exploit this condi- tion and many patients with conditions such as HIV or diabetes mellitus die due to complications. It is important for doctors to know in which cases they should monitor such other parameters as lung functions. © 2014 Polish Society of Allergology. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved. * Corresponding author at: Katedra Alergologii, Immunologii i Dermatologii Zakład Immunopatologii UM w Łodzi, ul. Żeligowskiego 7/9, 90-752 Łódź, Poland. E-mail address: rafal.pawliczak@csk.umed.lodz.pl (R. Pawliczak). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/alergo http://dx.doi.org/10.1016/j.alergo.2014.03.004 2353-3854/© 2014 Polish Society of Allergology. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.