Antibodies protect against substances prior to cell infection. Antibodies are produced by a type of white blood cell called a B cell (B lymphocyte). B cells develop from stem cells in bone marrow.When B cells become activated due to the presence of a particular antigen, they develop into cells called plasma cells.he antigen-binding site is the area of the antibody that recognizes the specific antigenic determinant and binds to the antigen. Since different antibodies recognize different antigens, antigen-binding sites are different for different antibodies.