• Describe the normal host defence mechanisms of the upper respiratory tract and the eye

there are innate and adaptive immunity responses

Ocular defence mechanisms include the following

there are enzymes in the eyes, tears, saliva and mucous membrane which degrade pathogens.

Lysozyme is an enzyme which cleaves peptidoglycan (often around bacteria)

lysozyme destroys gram positive bacteria easily as its outside. layer is peptidoglycan

however

Gram negative bacteria have an outer-layer around their peptidoglycan layer and therefore the lysozyme cannot effect the gram negative bacteria

Lactoferrin is an enzyme which binds to iron - starves bacteria + fungi, disrupts cell walls + antiviral