Diagram of humoral (antibody) immune response. Invading organisms are attacked by the Y-shaped antibody molecules. Antibodies attach to the invaders and make it easier for them to be destroyed by the immune system. At the top, invaders (gold) are eaten by a macrophage, which processes their antigens and presents them to a helper T-cell (purple). The helper cells then activate their corresponding B-cells (blue). These divide repeatedly and become plasma cells that produce vast quantities of antibodies (orange) that attack the invader (gold).