Frozen section of a mouse lymph node, adjacent to the previous one, but in this case stained with fluorescent antibody against B-cells (rabbit anti-mouse immunoglobulin). The cells within the primary follicle are uniformly stained, whereas only few stained cells are visible in the diffuse cortex. Stained cells are also visible within the HEV at the right (both T-cells and B-cells enter the node from the blood through these vessels)..