What is your problem what subject
I believe that the most common antibody switch is from IgM to IgG.
Class switching occurs by a mechanism called the class switch recombination binding. It is a biological mechanism that allows the class of antibody produced by an activated B cell to change during a process known as isotype or class switching. The mechanism changes a B cell's production of antibodies from one form to another, such as from the isotype IgM to the isotype IgG.
The charge by the nucleus of a atom has a negative charge.
The first known single-celled organisms appeared on Earth about 3.5 billion years ago, roughly a billion years after Earth formed. More complex forms of life took longer to evolve, with the first multicellular animals not appearing until about 600 million years ago.