An antibody(immunoglobulin)is a Y shaped protein that is released during an immune response. It has a specific shape that recognizes a specific antigen(foreign or non-self protein) for example, bacteria or virus and attaches to it. The foreign protein is then either neutralized directly or tagged for attack by other parts of the immune system. Plasma cells are white blood cells that produce antibodies. Some directly go into the blood and some are bound by membranes and attach to B cells. This causes the B cells to manufacture more antibodies or to produce memory B cells. These will remain long after an infection and will confer immunity to a particular antigen if it is ever encountered again.