Latch onto toxic substances that bacteria produce and inactivate these toxic substances. Coat the bacteria. This action attracts other immune cells to destroy the invaders. Latch onto a virus so the virus cannot infect the body's cells. Cells present the virus to helper T cells that can recognize it.
Helper cells mature and multiply rapidly to fight off the virus.
They activate cytotoxic T cells who find and destroy the virus infected cells. They flare up unpredictably. The cellular immune system keeps them down. When this is not adequate, the body produces antibodies to the virus. When antibodies are high, it means the virus is not controlled.