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Abstract
In this work we investigated immunological mechanisms involved in the onset of PE, a multifactorial pregnancy related disease of global importance. The clinical symptoms range from de novo hypertension, renal and hepatic damage, to IUGR and convulsions (eclampsia). An imbalance between vasospastic and vasodilatory mediators, leading to generalized endothelial dysfunction, is most probable responsible for the onset of the disorder. Autoimmune reactions provoked by the semi-allogen fetus have also been postulated as a possible cause. Preterm delivery is the only curative therapie available.
Our focus was on a subset of B lymphocytes, the CD19+ CD5+ B1-a B cells. These cells belong to the innate immune system and produce natural polyreactive (and possibly autoreactive) antibodies such as AT1-AA but also different cytokines. In the context of PE it has been reported that B1-a B cells in the peripheral blood are augmented. Female sex hormones, pregnancy associated hCG and its isoform h-HCG modulate the immune functions in pregnancy and thus may be involved in the development of PE. Cytokine production patterns of B1-a B cells and the impact of female sex hormones were analyzed.
For our experiments an established mouse model for immunological pregnancy loss (CBA/J x DBA/2J model) was used. Aditionally, isolated human peripheral blood B1-a B cells were used.
In the mouse model we could demonstrate that in vivo transferred B1-a B cells induced deposits in the mothers’ kidneys, correlating with renal damage. Secretion patterns of the cytokines IL10, IFN-γ, TNF-α and IL17 in disturbed pregnancies were altered as measured by FACS or MBAA respectively. Our data revealed an increased expression of anti-inflammatory IL10 in normal pregnant mice.
The activation levels of human and murine B1-a B cells (as recorded by CD69 and CD86 expression) were influenced by female sex hormones in a dose-dependent manner. In humans, recombinant h-HCG had a strong capacity to activate B1-a B cells. PG exerted a comparable effect on murine B1-a B cells.
We provide further evidence for a possible autoimmune component in the pathogenesis of PE. B1-a B cell involvement might include AA secretion as well as cytokine production. H-HCG emerges as a potentially important factor for human B1-a B cell activation in vitro.