**2. The innate immune system in** *Leishmania* **infection and disease**

The innate immune response is the host's first line of defense against invading pathogens and consists of physical (e.g., skin), chemical (e.g., nitric oxide and reactive oxygen species), soluble factors (e.g., complement, chemokines and cytokines) and cellular defenses (e.g., neutrophils and macrophages), all of which play a vital role in determining the course of infection.
