original article Killer-cell immunoglobulin-like receptor and human leukocyte antigen-C genes 1 1 3 Summary Background We aimed herein to investigate the killer-cell immunoglobulin-like receptor (KIR) genes and human leukocyte antigen (HLA)-C alleles in patients with com- mon variable immunodeficiency (CVID), and to reveal their differences from those in healthy population. Methods In all, 18 patients who have been diag- nosed with CVID and 15 living donors of kidney trans- plant recipients were enrolled in the study. Polymerase chain reaction-sequence-specific primer (PCR-SSP) typ- ing method was used in molecular genetic analysis. e frequencies of the genes in the study groups were sta- tistically compared with each other using chi-square or Fisher exact tests, whichever were appropriate. Results Although there was no significant difference between both study groups with respect to distribution of KIR and HLA-C2 group genes, HLA-Cw7 allele frequency in patients with CVID was significantly lower than that in healthy population (P = 0.008). Conclusion is present study results support that HLA-Cw7 allele, an inhibitor of KIR ligand, may play a role in the pathogenesis of CVID. Keywords Killer-cell immunoglobulin-like receptor · Common variable immunodeficiency · Human leuko- cyte antigen-C alleles Introduction Common variable immune deficiency (CVID) is a het- erogeneous disease, characterized by defect in antibody production and recurrent bacterial infections [1]. Besides autoimmunity and allergy, the risk of cancer development was also found to be increased in natural course of this dis- order. In recent studies, a few mutations were shown in a small percentage of patients with CVID [2]. ese genetic defects were determined in the genes inducible T-cell costimulator on chromosome 2q (ICOS), transmembrane activator and CAML interactor on chromosome 17p (TACI), B-cell activating factor on chromosome 22q (BAFF), and CD19 (on chromosome 16p). e studies investigating the role of inheritance in CVID revealed that while familial transmission pattern of disease are seen in only approxi- mately 10 % of patients, sporadic pattern of disease occurs in most of the patients [3, 4]. On the other hand, lymphocyte subgroup analyses of patients with CVID showed decreased absolute num- ber and percentage of natural killer (NK) cells, which is assessed as increased susceptibility to cancer [5]. It is well known that NK cells are one of the cells responsible for a mode of defense mechanism called immune surveil- lance against the development of cancer [6]. However, the roles of NK cells in the development of cancer not only are based on their absolute number, but also dete- riorate the balance between surface expressions of their inhibitor and activator receptor that leads to decreased cytotoxic activity [7, 8]. ese receptors belong to the family of killer-cell immunoglobulin-like receptor (KIR) and C-type lectin [9]. Although the ligands of inhibitor receptors are HLA class 1 molecules, the ligands of acti- vator receptors have not yet been definitively found. In this study, we aimed to determine the distribution of KIR genes and HLA-C alleles encoding KIR ligands in patients with CVID and healthy donors, and to reveal whether these genes are associated with CVID. Dr. O. Kartal, MD () · Prof. U. Musabak · S. Yesillik, MD · R. I. Sagkan · A. Pekel · F. Demirel, MD · A. Baysan, MD · A. Selçuk, MD · Assoc. Prof. M. Güleç · Prof. O. Şener Division of Immunology and Allergic Diseases, Gulhane Military Medical Academy and School of Medicine, 06018 Ankara, Turkey e-mail: okartal@gata.edu.tr Received: 25 July 2014 / Accepted: 16 February 2015 © Springer-Verlag Wien 2015 Wien Klin Wochenschr DOI 10.1007/s00508-015-0769-8 Killer-cell immunoglobulin-like receptor and human leukocyte antigen-C genes in common variable immunodeficiency Ozgur Kartal · Ugur Musabak · Sait Yesillik · Rahsan I. Sagkan · Aysel Pekel · Fevzi Demirel · Abdullah Baysan · Ali Selçuk · Mustafa Güleç · Osman Şener