How does the mammalian immune system work?

The first line of defense is the innate immune system, which attacks invaders indiscriminately and consists of skin, mucus, and macrophages (white blood cells that engulf and digest foreign substances).

The immune system also has an adaptive immune system, which involves the creation of antibodies by B-cells, chemicals that facilitate the destruction of bacterial cells.

Memory B and T-cells that are created in the primary immune response (first exposure to a pathogen) are stored in the lymph nodes and can be used in subsequent exposures to more quickly create antibodies.