The density of two types of these cells forms the basis of a classification scheme proposed by Jérôme Galon, which ranges from I0 to I4 and may outperform traditional TNM staging. A type of these cells requires B7 proteins (-5[1])to provide costimulatory signals that prevent incomplete activation, which can lead to anergy. A type of these cells begins to express FOXP3 after receiving intermediate strength signals during negative selection. These cells, which include a “regulatory” subtype, have receptors (10[1])that bind to MHCs (-5[1])found on antigen-presenting cells. CD4-positive and CD8-positive (10[1])types (-5[1])of these cells, which mature in the thymus, (10[1])are respectively known as these cells’ helper and killer (10[1])varieties. (-5[1])For 10 points, the adaptive (10[1])immune system primarily consists of B cells and what other white blood cells? ■END■ (10[2])