Question

Describe some of the innate barriers and chemicals that exist that protect us from pathogens.

Answer 1

the innate or the non specific immune system has got so many barriers both physically (externally) and internally to protect us from the pathogen. These barriers are being classifie into four types

Anatomical, Physiological, Phagocytic and Inflammatory barriers. the anatomical and physiological constitute the first line of defense whereas phagocytic and inflammatory constitute the second line of defense. The third line of defense is the adaptive immunity.

Anatomical barriers are the structures present in our body which prevents the entry of the pathogen. For ex- Skin, hair, cilia, mucous membranes, pH (vaginal pH-acidic is microbicidal for many pathogens).

Physiological barriers are the physiological or metabolic processes in our body that helps in killing the bacteria. for ex- high temperature-fever, acidic pH of the stomach-HCl secretions, urine-uric acid, tears- lysozyme kills some of the bacteria.

Phagocytic barrier is produced by the phagocytic cells such as blood monocytes, macrophages and neutrophils. They engulf the pathogen or the antigen through endocytosis and digest them in coordination with the lysosome (by forming phagolysosome)

Inflammatory barrier includes some chemical signals in response to tissue damage which brings in phagocytic cells.

When any tissue is damaged either by microbial toxin or injury, the damagesd tissues release histamines. Histamines cause vasodilation and decrease the flow of blood. This facilitates the phagocytes to settle at the site of damage. They release chemokines which attracts lot more neutrophils (phagocytes). Phagocytes kill the pathogens. By doing so, the infection is restricted to the damaged area and the causative agent is killed.

Other than this there are some chemical mediators that aid in eliminating the pathogen. For ex- Interferons- spreads antiviral property to the cells not infected by virus, cascade of complement system, etc.