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1/ All B cells have the immunoglobulins IgM and IgD on their cell surface. The DNA contains both the information to create these two classes of immunoglobulins. They will be produced in equal amounts during the B cell development. 
2/ Once a B cell is activated toward a pathogen, it will begin to secret immunoglobulins (antibodies) in the form of the IgM. This is the only thing it is able to create and secret at this point.
