In placental mammals there are five antibody Isotypes known as IgA, IgD, IgE, IgG, and IgM.
Isotype or class switching is a biological process
occurring after activation of the B cell, which allows the cell to produce different classes of antibody IgA, IgE, or IgG.
Each Isotype is adapted for a distinct function;
therefore, after activation, an antibody with an IgG, IgA, or IgE effector function might be required to effectively eliminate an antigen.