Yaygın Değişken İmmün Yetmezlik Tanılı Hastalarda LRBA Defektinin Araştırılması

Abstract

ABSTRACT Çağdaş Ayvaz, DN. Investigation of LRBA defect in patients with common variable immunodeficiency, Institute of Health Sciences, Program of Immunology, PhD. Thesis, Ankara, 2017. Primary immunodeficiencies are extremely heterogeneous group of disorders generally caused by Mendelian inheritance. "Common Variable Immunodeficiency” (CVID) is considered as one of the most common disease of the primary immune deficiencies. It is characterized by primary antibody deficiency and lack of antibody response. The LRBA defect, which was defined after 2012, is one of the defects to be considered in patients with hypogammaglobulinemia, antibody deficiency and especially those with autoimmune and inflammatory bowel disease-like findings. The aim of our study was to investigate LRBA mutations which are thought to be genetic cause of the disease in gene and protein level, in patients with CVID, who admitted to the Pediatric Immunology Unit with hypogammaglobulinemia and autoimmunity. Thirty patients who were admitted to the Pediatric Immunology Unit and having clinical features of hypogammaglobulinemia, lymphoproliferation and autoimmunity were evaluated for LRBA gene defect. In three patients, by Western blot analysis protein absence is shown and in four patients by Sanger sequence analysis LRBA defect was shown. Totally in five patients LRBA was found to be defective in protein and/or gene level. In addition to thirty patients, the defect site was also assessed by Sanger sequence analysis in the siblings of patients with known LRBA gene defects and in HLA-matched related donors. Some donors were also assessed at the protein level by Western blot analysis. While heterozygosity was detected in some of the siblings and donors, homozygous defects were not found. In addition, post-transplant LRBA protein expression in a patient with stem cell transplantation was compared with pre-transplant expression by Western Blot analysis. It was determined that the expression was increased after the transplantation. A total of five patients, including two which was diagnosed with our study were planned to be treated with hematopoietic stem cell transplantation (HSCT) from their HLA-compatible donors who were found to have no LRBA defect by our study, HSCT is performed in four, one is diseased in the follow-up. When the clinical status of patients with LRBA defects is evaluated, it is seen that the disease is very severe and fatal when transplantation is not performed. Therefore, it is clear that patients with CVID and ALPS phenotypes should be evaluated rapidly for this defect. In this study, it can be seen that if we want to compare the disease-related genotype phenotype correctly, LRBA-related research only performed at the protein level can lead to incorrect results. For this reason, both genetic and protein level research should be the aim. In addition, the risk of degradation must be predicted during Western Blot analysis as the molecular weight of the LRBA protein is high. As a result of our study, the molecular defects in two patients were confirmed by both protein analysis and sequence analysis. Other patients who have no defects to explain their disease need to be evaluated with next-generation genome sequencing. Genetic defects that may cause CVID disease should be evaluated by gene panels or by whole genome sequencing.