So we have this antigen MHC class Two complex that forms. Now, as soon as this actually takes place we have a special type of T lymphocyte whose membrane contains a special glycoprotein known as CD four. Only T lymphocytes that contain the CD four glycoprotein can actually go on and bind onto the antigen MHC class II complex. So for example, we have some type of inactivated helper T cell that contains the CD four glycoprotein on the membrane goes on and binds onto this complex of the macrophage. And once this binding process takes place that ultimately activates the helper T cell. And that also releases many different types of chemicals involved in our immune system and that activates T cells.