Expression of P2X₇ receptor in human tonsil by immunohistochemistry. Serial cryostat sections were processed to show the location of P2X₇ receptors using the anti-P2X₇ receptor MoAb. (A and B) Irrelevant isotype (IgG2b) control MoAb; (C and D) anti-P2X₇ MoAb; (E and G) anti-CD3 (showing T cells) and anti-CD20 (showing B cells). (B), (D), (F), and (H) are higher magnifications of (A), (C), (E) and (G), respectively. GC, germinal center; MZ, marginal zone; T, T-cell zone. Inset in (D) shows a higher magnification of one of the positive cells in the marginal zone to detail the morphology.