Which of the following is NOT a barrier under innate immunity?

Innate immunity is a non-specific type of defense mechanism that is present at the time of birth. It consists of four main types of barriers:
Physical barriers (e.g., skin, mucus membranes)

Physiological barriers (e.g., acid in stomach, saliva in mouth, tears)

Cellular barriers (e.g., leucocytes, macrophages)

Cytokine barriers (e.g., interferons)

'Mental barriers' have no scientific relation to the biological immune response framework.