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 to provide costimulatory signals that prevent incomplete activation, which can lead to anergy. A type (10[1])of these cells begins to express FOXP3 after receiving intermediate (-5[1])strength signals during (10[1])negative selection. These cells, which include a “regulatory” subtype, have receptors (10[1])that bind to MHCs found on antigen-presenting (-5[1])cells. CD4-positive and CD8-positive types (10[1])of these cells, which mature in the thymus, (10[1])are respectively (10[1])known as these cells’ helper (-5[1])and (10[1])killer varieties. For 10 points, the adaptive immune system primarily consists of B cells and what other white (10[1])blood cells? (10[1])■END■ (10[1])