Previously we focused on B lymphocytes which are the cells that make up our humoral immunity. Now let's focus on T lymphocytes or T cells which are the white blood cells that make up our cell mediated immunity of our adaptive immune system. Now, just like B cells T cells also have special receptors on the membrane we call T cell receptors. And because there are two different types of T cell receptors we categorize T lymphocytes into two categories. We have AlphaBeta T cells which consist of special T cell receptors that have an alpha and a beta polypeptide subunit. And we also have gamma delta T cells which contain T cell receptors that consist of a gamma and a delta polypeptide subunit.