Figure 1. Three proposed roles for CD20⁺ tumor-infiltrating lymphocytes (TILs) in promoting anti-tumor immunity. (A) CD20⁺ TILs as antigen presenting cells. B cells can bind tumor antigens via surface Ig molecules, process them and then present peptides to CD8⁺ and CD4⁺ T cells via MHC Class I and Class II, respectively. (B) CD20⁺ TILs as lymphoid organizers. B cells are able to secrete lymphotoxin, which can induce stromal cells to express adhesion molecules, cytokines and chemokines. These factors, in turn, can recruit and retain other lymphocytes. (C) CD20⁺ TILs as polarizing cells. Type-I and Type-II B effector cells (Be1 and Be2) can secrete cytokines such as interferon γ (IFNγ) and interleukin-4 (IL-4), which can skew T-cell responses toward Th1, Th2 or other functional states.