More than half of primary immune deficiencies are associated with impaired antibody production with mechanisms for disease being still largely unknown. First signs are most often expressed in childhood and early diagnosis is important for starting appropriate treatment and preventing severe infections. Functional activation tests of B cells are important to assess function of humoral immune system in patients with primary immune deficiency. Based on in vitro functional test for determination of proliferation potential, differentiation into plasmablast and immunoglobulin secretion after stimulation of B cells with CpG, we can reliably assess the ability of B cells to be activated. CpG activates B lymphocytes in a T cell-independent pathway. Proliferation is determined by measuring incorporation of fluorescently labelled EdU in DNA of dividing cells. We have shown that after stimulation B cells proliferate, differentiate into plasmablasts, and secrete immunoglobulins in healthy individuals. However, in patients with primary immune deficiency diagnosis, proliferation of B cells, plasmablast differentiation or immunoglobulin secretion is reduced or absent. To introduce in vitro function test in routine, we determined optimal conditions for stimulation of B cells with CpG. We also determined normal values of proliferation of B cells, naïve and memory B cells and plasmablasts in healthy individuals for adults and children.
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