Year: 2018
Type: dissertation
Abstract: Introduction and aims: Common variable immunodeficiency (CVID) is a heterogenous primary immune deficiency disorder characterized by recurrent infections, defective B cell differentiation and decreased levels of switched immunoglobulins (Igs) like IgG and IgA. Many CVID patients have vitamin A deficiency, which may contribute to their high infection risk. B cells from CVID patients also frequently present with defective toll like receptor (TLR) 9 signaling. TLR9 is part of the innate immune system, and is activated by microbial DNA, which is rich in unmethylated CpGs. In vitro, CpG oligodeoxynucleotides (CpG-ODN) are used to stimulate the receptor. RP105 also belongs to the TLR receptor family and synergizes with TLR9-signaling. Our lab has previously demonstrated that the vitamin A metabolite retinoic acid (RA) is able to enhance the immunostimulatory effects of TLR9- and RP105-signaling, both in normal and CVID-derived B cells. They have also identified a subgroup of CVID patients with TLR9/RP105-stimulated B cells expressing high levels of IRF4 and low levels of AICDA combined with a poor response to RA in terms of enhanced expression of these plasma cell related genes. The aims of this master thesis were 1. To confirm the existence of the CVID-subpopulation with IRF4highAICDAlow-expressing B cells, and 2. To assess a possible correlation between the subgroup of CVID patients characterized by IRF4highAICDAlow-expressing B cells, and the patients with B cells that respond poorly to RA in terms of enhanced TLR9/RP105-mediated secretion of IgG and/or IgA. Methods: CD19+ B cells were isolated from whole blood collected from 10 healthy controls and 10 CVID patients, and the cells were stimulated with CpG-ODN and anti-RP105 with or without RA. ELISA assays were performed to analyze the effects of the stimulants on IgG and IgA secretion, and FAST rt-qPCR was performed to analyze the expression of the four plasma cell related genes AICDA, IRF4, BCL6 and PRDM1. The data from these two analyzes were then combined to reveal any correlations between the gene expression profiles and the secretion of IgG and IgA in response to RA-stimulation. Results: RA was able to enhance TLR9/RP105-mediated IgG and IgA levels in both normal and CVID-derived B cells. The effects of RA varied considerably, in particular between B cells derived from different CVID patients. Results of the specific aims: 1. We identified the subpopulation of CVID patients with B cells expressing high IRF4 and low AICDA levels. The patients belonging to this group also had a poor response to RA in terms of enhancing the TLR9/RP105-mediated expression levels of IRF4 and AICDA. 2. There were no correlations between the B cells from the identified subpopulation of CVID patients, and CVID-derived B cells with the lowest response to RA in term of IgG/IgA secretions. Thus, we observed both relatively high and low/no RA-enhanced secretion of TLR9/RP105-induced IgG and IgA in the IRF4highAICDAlow-expressing subpopulation of B cells from CVID patients. Conclusions: The expression profiles of IRF4 and AICDA based on in vitro stimulation of CVID-derived B cells seem not to predict which patients that would benefit from supplementation of vitamin A. However, the results of the present thesis support our previous suggestion that some CVID patients most likely will benefit from vitamin A supplementation to enhance their serum levels of IgG and/or IgA. In order to optimize the treatment of CVID patients, further studies should be conducted to distinguish the RA responding subpopulation of CVID patients from the non-responders.
Author: Ida Guttormsen
Language: English
Subfield: Immunology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2891997384