2). is proposed under the premise of a “protein homeostasis system”; where innate and adaptive immune cells control pathogenic proteins that are harmful to host cells at a molecular level. After an infection of unknown KD pathogen(s), the pathogenic proteins produced from an unknown focus, spread and bind to endothelial cells of coronary arteries as main target cells. To control the action of pathogenic proteins and/or substances from the hurt cells, immune cells are activated. Initially, non-specific T cells and non-specific antibodies are involved in this reaction, while hyperactivated immune cells produce numerous cytokines, leading to a cytokine imbalance associated with further endothelial cell injury. After the emergence of specific T cells and specific antibodies against the pathogenic proteins, tissue injury ceases and a repair reaction begins with the immune cells. Keywords: Kawasaki disease, coronary artery lesions, laboratory parameters, intravenous immunoglobulin, non-responders, pathogenesis, (S)-2-Hydroxy-3-phenylpropanoic acid treatment INTRODUCTION Kawasaki disease (KD) is usually a self-limiting systemic inflammatory disease that occurs predominantly in children more youthful than 5 years of age.1 Clinical manifestations of KD include prolonged fever (1-2 weeks, mean 10-11 days), conjunctival injection, oral lesions, polymorphous skin rashes, extremity changes, and cervical lymphadenopathy, all of which comprise diagnostic criteria. In addition, arthritis, aseptic meningitis, anterior uveitis, gall bladder hydrops, urethritis and lung involvement can be seen. 2 Some more severely affected patients show cardiac complications, particularly coronary artery lesions (CALs) such as aneurysms and ectasias, which develop in approximately one quarter of untreated children and 5-10% of intravenous immunoglobulin (IVIG) treated children.3,4 These diverse systemic inflammations (mainly vasculitis) may be caused by inflammatory mediators with circulating immune cells (neutrophils, lymphocytes, natural killer cells and monocytes), and there may be various immune cell infiltrations in all affected pathologic lesions from affected lymph nodes to skin rashes. Particularly, a larger quantity of T cells (more CD8 cells than CD4 cells), large mononuclear cells, macrophages and plasma cells, with a smaller quantity of neutrophils, are observed in various organ tissues of fatal cases of acute KD.5-8 In addition, peripheral blood analysis of acute KD patients showed T lymphocytopenia with depressed CD8 T cells, increased activated CD4 T cells and depressed CD4+CD25+ regulatory T cells.9-11 These findings suggest that the majority of circulating T cells move to the pathologic lesions of various tissues in acute KD. Therefore, circulating immune cells, especially T cells, control the inflammation of the majority of the affected regions of KD patients without sequelae, but they also may be involved in the progression of the disease, such as in the case of CALs. Epidemiological and clinical data suggest that KD is an immunological reaction to infectious triggers occurring in genetically susceptible children. Although studies have provided hypothetical explanations for the pathogenesis of KD, the etiologic brokers, the immunopathogenesis of the vasculitis, and the mechanism that underlies the predilection for coronary artery involvement in KD are largely unknown.2,11-16 Laboratory parameters are used for the diagnosis and evaluation of conditions of patients for any inflammatory disease. As for laboratory findings in KD, many inflammatory indices switch throughout the (S)-2-Hydroxy-3-phenylpropanoic acid disease process; elevated levels of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), leukocyte count with neutrophilia (lymphopenia), platelet count, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and other inflammation associated enzymes, as well as decreased levels of lymphocytes, albumin, hemoglobin, sodium, potassium and total cholesterol including high density lipoprotein cholesterol (HDL-cholesterol) have been detected.2 The severity of inflammation in KD is reflected by inflammatory parameters; thus, laboratory findings are helpful for diagnosing incomplete KD and evaluating (S)-2-Hydroxy-3-phenylpropanoic acid patients for early prediction of IVIG non-responsiveness. Although some score systems for early detection of IVIG non-responders with a higher risk of CALs have been developed,17,18 further studies are needed for the early detection and proper treatment of initial IVIG nonresponders. In this article, a brief review of the epidemiologic, clinical and laboratory characteristics of KD, as well as the policy of our institution for initial IVIG nonresponders according to the changes in laboratory findings after IVIG infusion are launched. We also propose a new concept for (S)-2-Hydroxy-3-phenylpropanoic acid the immunopathogenesis for KD under the BCL2L5 premise of a “protein homeostasis system” of the host. EPIDEMIOLOGIC AND ETIOLOGIC.