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Cross-linking of surface IgM activates NF-kappa B in B lymphocyte
J W Rooney1, P M Dubois, C H Sibley
1Department of Genetics (SK-50), University of Washington, Seattle 98195.
Insights
Cross-linking surface IgM rapidly activates NF-kappa B (nuclear factor kappa B) in B cells. This process occurs quickly and does not require protein kinase C (PKC) activation.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- B lymphocytes utilize surface IgM for activation, influencing cell cycle and differentiation.
- Nuclear factor kappa B (NF-kappa B) activation and nuclear translocation are common responses to stimuli in B cells and B cell tumors.
Purpose of the Study:
- To investigate whether cross-linking of surface IgM triggers NF-kappa B activation.
- To elucidate the signaling pathway involved in NF-kappa B activation by surface IgM.
Main Methods:
- Utilized murine B lymphoid cell lines (70Z/3, M12) and splenic cell fractions.
- Stimulated cells with cross-linking anti-IgM antibodies.
- Assessed NF-kappa B activation and nuclear translocation.
- Investigated the role of protein kinase C (PKC) by depleting it using phorbol 12-myristate 13-acetate.
Main Results:
- Cross-linking surface IgM with anti-IgM antibodies rapidly activated NF-kappa B in B cells.
- Optimal antibody doses and 5-10 minutes were required for maximal NF-kappa B activation.
- Depletion of functional PKC did not prevent NF-kappa B nuclear translocation following IgM cross-linking.
Conclusions:
- Surface IgM cross-linking is a potent and rapid inducer of NF-kappa B nuclear translocation in B cells.
- The activation pathway for NF-kappa B induced by IgM cross-linking is independent of PKC activation.
Abstract:
In B lymphocytes, cross-linking of surface IgM activates changes in both the cell cycle and differentiation. In normal B cells and B cell tumors, many stimuli induce the activation of NF-kappa B and its translocation from the cytoplasm to the nucleus. In this study we sought to determine if cross-linking of surface IgM led to the activation of NF-kappa B. Our results show that activation of B cells by cross-linking anti-IgM antibodies activated NF-kappa B in the murine B lymphoid cell lines 70Z/3 and M12, and in the dense fraction of splenic cells. The activation of NF-kappa B required optimal doses of anti-IgM antibodies and took 5 to 10 min to reach maximal levels. Cross-linking of IgM has also been shown to activate protein kinases including protein kinase C (PKC). To test whether PKC activation was required for NF-kappa B translocation, we treated 70Z/3 cells for 18 h with phorbol 12-myristate 13-acetate, a procedure which depletes these cells of functional PKC. This treatment did not abrogate the nuclear translocation of NF-kappa B following anti-IgM cross-linking. These results indicate that the nuclear translocation of NF-kappa B is rapidly induced by surface IgM cross-linking and that this activation appears to use a pathway which does not require PKC.
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