by Shiu Kar Chi. / Thesis (M.Sc.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 61-67). / Abstract also in Chinese. / ACKNOWLEDGEMENTS / ABSTRACT / LIST OF TABLES / LIST OF FIGURES / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Overview --- p.2 / Chapter 1.2 --- Historical perspective --- p.2 / Chapter 1.3 --- Biochemistry of the IgG subclasses --- p.4 / Chapter 1.4 --- IgG subclasses and human diseases --- p.7 / Chapter 1.4.1 --- Glomerulonephritis --- p.7 / Chapter 1.4.2 --- Blistering skin lesions --- p.7 / Chapter 1.4.3 --- Insulin dependent diabetes mellitus (IDDM) --- p.8 / Chapter 1.5 --- Primary antibody deficiencies --- p.8 / Chapter 1.5.1 --- CVID --- p.8 / Chapter 1.5.2 --- X-linked antibody deficiency --- p.8 / Chapter 1.5.3 --- IgG subclass deficiency --- p.10 / Chapter 1.5.4 --- Specific antibody deficiencies --- p.10 / Chapter 1.5.5 --- Selective IgA deficiency --- p.10 / Chapter 1.6 --- IgG subclasses deficiency --- p.10 / Chapter 1.7 --- Clinical manifestation of IgG subclass deficiency --- p.11 / Chapter 1.8 --- Restriction of IgG subclass responses to exogenous antigens --- p.12 / Chapter 1.9 --- Expression of IgG subclasses --- p.14 / Chapter 1.10 --- Mechanisms of IgG subclass deficiency --- p.14 / Chapter 1.10.1 --- Gene deletion --- p.14 / Chapter 1.10.2 --- Immune dysregulation --- p.17 / Chapter 1.10.2.1 --- T-cell receptor defects --- p.18 / Chapter 1.10.2.2 --- Interferon gamma (IFN-y) --- p.18 / Chapter 1.10.2.3 --- Interleukin-4 (IL-4) --- p.19 / Chapter 1.10.2.4 --- Interleukin-6 (IL-6) --- p.19 / Chapter 1.11 --- Prevalence of IgG subclass deficiency --- p.19 / Chapter 1.12 --- Reference intervals for IgG subclass --- p.20 / Chapter 1.13 --- Methods for investigation of IgG subclass deficiency --- p.20 / Chapter 1.13.1 --- Radial-immunodiffusion --- p.21 / Chapter 1.13.2 --- Enzyme linked immunsorbent assay --- p.21 / Chapter 1.13.3 --- Nephelometry/turbidmetry --- p.21 / Chapter 1.14 --- Aim of study --- p.22 / Chapter CHAPTER 2 --- MATERIALS AND METHOD I The Binding Site IgG Subclass Assay --- p.23 / Chapter 2.1 --- Materials --- p.24 / Chapter 2.1.1 --- IgG subclass assay --- p.24 / Chapter 2.1.2 --- Evaluation of patients immune status --- p.24 / Chapter 2.1.3 --- Apparatus and equipment --- p.24 / Chapter 2.2 --- Evaluation of The Binding Site human IgG subclass assay on Beckman Array 360 protein system --- p.25 / Chapter 2.2.1 --- Principle of the Beckman Array Protein System --- p.25 / Chapter 2.2.2 --- Assay preparation and procedure --- p.25 / Chapter 2.2.3 --- Performance characteristic of the IgG subclasses assay --- p.28 / Chapter 2.2.3.1 --- Gain setting --- p.28 / Chapter 2.2.3.2 --- Within batch precision --- p.28 / Chapter 2.2.3.3 --- Interassay precision --- p.28 / Chapter 2.2.3.4 --- Linearity of the assay --- p.29 / Chapter 2.2.3.5 --- Interference of the IgG subclass assay --- p.29 / Chapter 2.2.3.6 --- Recovery experiment --- p.30 / Chapter CHAPTER 3 --- MATERIALS AND METHOD II IgG Subclass Deficiency in Hong Kong --- p.32 / Chapter 3.1 --- Patients and controls --- p.33 / Chapter 3.2 --- Blood samples --- p.33 / Chapter 3.3 --- Serum total haemolytic complement and alternative pathway haemolytic complement assay --- p.34 / Chapter 3.3.1 --- Total haemolytic complement --- p.34 / Chapter 3.3.2 --- Alternative pathway haemolytic complement --- p.34 / Chapter 3.4 --- Statistical analysis --- p.35 / Chapter CHAPTER 4 --- RESULTS I: Evaluation of The Binding Site IgG Subclass Array Kit --- p.36 / Chapter 4.1 --- Gain setting --- p.37 / Chapter 4.2 --- Within batch precision --- p.37 / Chapter 4.3 --- Inter-assay precision --- p.37 / Chapter 4.4 --- Linearity and lowest limit of detection --- p.37 / Chapter 4.5 --- Interference experiments --- p.37 / Chapter 4.6 --- Recovery experiment --- p.37 / Chapter CHAPTER 5 --- RESULTS II: IgG Subclass Deficiency in Hong Kong --- p.45 / Chapter 5.1 --- IgG subclass concentrations and humoral immune status evaluation results of patients and control subjects --- p.46 / Chapter 5.2 --- Statistical tests --- p.45 / Chapter CHAPTER 6 --- DISCUSSION I: The Binding Site IgG Subclass Array Kit --- p.52 / Chapter 6.1 --- IgG subclass assays --- p.53 / Chapter 6.2 --- Within batch and inter-assay precision --- p.53 / Chapter 6.3 --- Lowest limit of detection --- p.53 / Chapter 6.4 --- Interference --- p.54 / Chapter 6.5 --- Recovery of IgG --- p.54 / Chapter 6.6 --- Overall performance of the nephelometric assay --- p.55 / Chapter CHAPTER 7 --- DISCUSSION II: IgG Subclass Deficiency in Hong Kong --- p.56 / Chapter 7.1 --- IgG subclass deficiency in adults --- p.57 / Chapter 7.2 --- Paetiatric patients --- p.59 / Chapter 7.3 --- Recurrent infections and IgG subclass deficiency --- p.59 / Chapter 7.4 --- Summary --- p.60 / REFERENCES --- p.61

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Levels of Immunoglobulin G (IgG)-subclasses are analyzed when patients have reoccurring infections and in order to follow the treatment of IgG4 related disease. The measured quantity of IgG-total can be within the reference interval even if the patient has a deficiency in one of the IgG-subclasses. Due to this Sundsvall’s hospital plans to begin analyzing IgG-subclasses. The aim was to verify the performance level of the analysis IgG-subclasses (IgG1-4) with Siemens Atellica NEPH 630. The method was verified by evaluating the method’s precision and by comparing the sum of IgG-subclasses with the quantity of IgG-total analyzed on Cobas c502. In addition, the reference intervals provided by Siemens were evaluated using samples from blood donors. The study evaluated whether there was a correlation between infection with SARS-CoV2 and a deficiency in IgG-subclasses. The verification began by performing quality control twice daily over a period of four weeks. The IgG-subclasses test was performed on blood donor samples with Siemens Atellica NEPH 630 for evaluation of the reference values. The coefficient of variation was less than 6 % for all four subclasses. The reference values for IgG1, IgG2, IgG3, and IgG4 are all in alliance with the reference values provided by Siemens. The sum of IgG-subclasses corresponded well with IgG-total with a correlation value (R) 0.82. No correlation was found between IgG deficiency and infection with SARS-CoV2. The validation of the analysis of IgG-subclasses was successful with quality measurements within the supplier’s intervals. No adjustments will be needed for the reference intervals.