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Introduction: For a successful pregnancy, a set of physiological requirements has to be fulfilled. The mother has to provide enough nutrients and the proper anatomical environment for the developing fetus and protect him and herself against pathogens. The cells of the im-mune system constantly monitor the organism in search for pathogens and mount a response to eradicate the threat. The favourable outcome of an immune response re-lays on the capacity of those cells to recognize structures that shouldn’t be present in the organism and the speed or strength at which the cells react. During pregnancy, however, a fetus is able to establish a firm contact with the endometrium of the mother and then grow for an extended period of time. This “exception to the rule” hides behind a set of fine-tuned regulations of the immune responses which are not completely un-derstood. Though many cell types have been extensively investigated in the past dec-ades, B cells play yet enigmatic roles. The aim of this work is to uncover the events occurring within the B cell development during pregnancy and to study the role of certain subtypes in healthy pregnancy and pregnancy miscarriage. Methods: For all experiments, 8-weeks-old female mice either non-pregnant, having normal preg-nancies or miscarriage were used. Organs were removed and cells isolated using standard protocols. The analysis of the population distribution was performed by Flow Cytometry. For in vitro experiments, specific cell subsets were isolated using MACS Cell Separation. Bio-plex method was used for the assessment of Immunoglobulin isotypes in serum, while CBA Array was the method used to measure cytokine levels in the supernatant of cell cultures. Statistical analysis was done using GraphPad Prism software. Results: Pregnancy had a strong impact on the murine B cell development. The restructuration of the B cell compartment could be appreciated already from the bone marrow progeni-tors, reduced in pregnant mice. Peripheral subsets drastically adapted their develop-mental pathways, with a drift towards the generation of marginal zone B cells. B cells also showed functional adaptations to gravidity, as evidenced by the changes in the immunoglobulin production and immunomodulatory capacity. Conclusions: For the first time a deep investigation of the consequences of pregnancy on the B cell development was performed, covering several aspects of B cell functionality. This work shows that B lymphocyte compartment is remodelled during pregnancy. Aberration of this process may lead to pregnancy complications including miscarriage.
The immune system of all vertebrates primarily is responsible to maintain the organisms homeostasis by either eliminating neoplastic or altered body cells and to protect against foreign invaders (viruses, bacteria, fungi, parasites) (Murphy 2012). It is a highly regulated network of innate and adaptive mechanisms between humoral factors and leukocytes. The successful elimination or protection is crucially based on differentiation of self from non-self. Pathogens and altered body cells are recognized by different receptor complexes on immune cells. Expressed pathogen- or danger-associated molecular patterns (PAMPs or DAMPs, respectively) are bound by pattern recognition receptors (PRR) (Takeuchi and Akira 2010). Missing major histocompatibility (MHC) class I molecules or non-self (e.g. allogeneic or xenogeneic cells) MHC are recognized by natural killer cell receptors (Fischer, Koppang and Nakanishi 2013, Raulet 2006). Foreign non-self peptides are presented through MHC class I (intracellular) or through MHC class II (extracellular) to B- cell or T cell receptor complexes. This initial activation is regulated by humoral factors or cellular interactions (receptor-ligand interactions) resulting in the activation, proliferation and effector function within an immune response. Some of the cellular receptors are permanently expressed on all leukocytes on a high level (MHC class I), whereas others only are expressed during certain developmental or activation stages or on certain leukocyte populations (monocytes, granulocytes, NK cells, lymphocytes) (Murphy 2012, Biosciences 2010). For different mammals (man, mouse, rat, but also swine, cattle, dog), a system of characterized leukocyte surface molecules primarily based on the recognition of these molecules by specific monoclonal antibodies (mabs) was summarized at international workshops as clusters of differentiation (CD) (Cobbold and Metcalfe 1994, Hopkins, Ross and Dutia 1993, Haverson et al. 2001, Mason et al. 2001). Using these mabs, it is not only possible to characterize the developmental and functional stage of different leukocyte subpopulations but also to define the interactions between these populations. For bony fish, such a system does not exist. Only a limited number of mabs against leukocyte surface molecules is available and most of them are strongly specific for species (Köllner et al. 2004, Köllner et al. 2001, Zhang et al. 2010, Ramirez-Gomez et al. 2012, Wen et al. 2011, DeLuca, Wilson and Warr 1983, Toda et al. 2011, Toda et al. 2009, Takizawa et al. 2011a, Hetland et al. 2010, Araki et al. 2008). The goal of this PhD work, therefore, was to develop monoclonal antibodies against surface markers of rainbow trout (Oncorhynchus mykiss) T cell population (chapter 2). The lymphocytes are characterized by the expression of a T cell receptor complex composed of TCR chains (α and β) and CD3 chains (α, β, γ, δ, ε and ζ). Cytotoxic T lymphocytes (CTLs) binds to MHC class I bound peptide on the infected host cell using their T cell receptor (TCR) and its co-receptor CD8 resulting in specific killing. Th cells recognize peptides through their T cell receptor (TCR) and their co-receptor CD4 after extracellular antigens uptake, processing and presentation via MHC class II by professional antigen presenting cells (macrophages, dendritic cells and B cells). During recent years, genes encoding MHC class I and II, TCR and their co-receptors CD8 and CD4 have been cloned in several fish species and antibodies have been developed to study protein expression in morphological and functional contexts. However, mabs specific for TCR or CD3 have not been established yet. Therefore, using pan-T cell marker specific mabs, the activation and kinetics of T cell subpopulation should be investigated (chapter 2). Moreover, a flow cytometry method was established using different lineage marker specific mabs to measure different leukocyte populations and their involvement in immune mechanisms of trout using a single tube assay (chapter 3). The first line of defense against altered body cells or pathogens is provided by evolutionarily ancient macrophages and natural killer (NK) cells. These innate mechanisms are well developed in bony fish. Two types of NK cell homologues have been described in fish: non-specific cytotoxic cells and NK-like cells (Shen et al. 2002, Shen et al. 2003, Shen et al. 2004, Fischer et al. 2013). Functional assays for innate and adaptive lymphocyte responses have been developed in only a few fish species. However, there are no tools available until now in trout to follow these cells directly in the immune response. The molecular characteristics and the expression on leukocyte subpopulations of CD56 were therefore analyzed. Furthermore, a mab that is specific for a molecule expressed only in NK cells but with uncommon expression kinetics was established (chapter 4). Overall, the established tools and methods allow a more detailed characterization of cellular immune mechanisms against intracellular pathogens in rainbow trout.