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KCI등재 학술저널

CD40 Co-stimulation Inhibits Sustained BCR-induced Ca<SUP>2+</SUP> Signaling in Response to Long-term Antigenic Stimulation of Immature B Cells

CD40 Co-stimulation Inhibits Sustained BCR-induced Ca<SUP>2+</SUP> Signaling in Response to Long-term Antigenic Stimulation of Immature B Cells

Regulation of B cell receptor (BCR)-induced Ca<sup>2+</sup> signaling by CD40 co-stimulation was compared in long-term BCR-stimulated immature (WEHI-231) and mature (Bal-17) B cells. In response to long-term pre-stimulation of immature WEHI-231 cells to &#1345;-IgM antibody (0.5∼48 hr), the initial transient decrease in BCR-induced [Ca<sup>2+</sup>]<sub>i</sub> was followed by spontaneous recovery to control level within 24 hr. The recovery of Ca<sup>2+</sup> signaling in WEHI-231 cells was not due to restoration of internalized receptor but instead to an increase in the levels of PLC&#1347;2 and IP<sub>3</sub>R-3. CD40 co-stimulation of WEHI-231 cells prevented BCR-induced cell cycle arrest and apoptosis, and it strongly inhibited the recovery of BCR-induced Ca<sup>2+</sup> signaling. CD40 co-stimulation also enhanced BCR internalization and reduced expression of PLC&#1347;2 and IP<sub>3</sub>R-3. Pre-treatment of WEHI-231 cells with the antioxidant N-acetyl-L-cysteine (NAC) strongly inhibited CD40-mediated prevention of the recovery of Ca<sup>2+</sup> signaling. In contrast to immature WEHI-231 cells, identical long-term &#1345;-IgM pre-stimulation of mature Bal-17 cells abolished the increase in BCR-induced [Ca<sup>2+</sup>]<sub>i</sub>, regardless of CD40 co-stimulation. These results suggest that CD40-mediated signaling prevents antigen-induced cell cycle arrest and apoptosis of immature B cells through inhibition of sustained BCR-induced Ca<sup>2+</sup> signaling.

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