Abstract
The Protein disulphide-isomerase (PDI, EC 5.3.4.1, Thiol-proteindisulphide oxidoreductase, EC 1.8.4.2) is thought to regulate the sulfhydryl status of cells and to catalyze thiol/disulphide exchange reactions involved in the post-translational processing of disulphide containing secretory proteins. The aim of the present investigations was to study the possible function of this enzyme in differentiation of B lymphocytes and immunoglobulin synthesis. Non-adherent human mononuclear cells or purified T cells were cultured in presence and absence of Pokeweed mitogen over 3, 5 and 7 days. Monoclonal antibodies and a rabbit polyclonal antiserum specific for human liver PDI were produced to determine the concentration of PDI by an ELISA technique and cytoplasmic immunofluorescence. After PWM stimulation, both, the cellular content of PDI as well as that of immunoglobulin, particularly IgM, have been found to be induced in a time dependent manner with a 2-3fold increase in comparison to unstimulated cells. The specific induction of PDI in human B lymphocytes was also confirmed in Western blotting.
Our findings suggest that PDI plays a critical role in the final stages of B cell differentation and immunoglobulin synthesis by activated B cells and plasma cells, respectively.
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