Question

What immune system obstacles would bacteria encounter as they make initial contact with the skin of a hand and then enter the body through a cut in the skin? Discuss these obstacles in the order that the bacteria would encounter them.  Don't forget the adaptive immune response - be specific about antigen presenting cells, B cells, T cells.

You should have 3 barriers to discuss.

Answer 1

A bacteria (pathogen) has to encounter three barriers in prder to penetrate inside a body. They are discussed as follows:

1. Physical Barriers- It involves skin, as it is made of stratified squamous epithellium and the upper layer, whichis called epidermis consist on closely packed cells and the upper layers also contais dead cells. This closed structure does not allow bacteria to enter inside easily.

2. Non-Specific Barrier- It is also known as Innate immunity, which is possessed by an organism since their birth. This barrier directly kills the invaders rather than targetting them specifically. It involves various phagocytic cells such as macrophages, neutrophils, etc. They kills the foreign pathogen by phagocytosis. Other ways to kill a pathogen is inflammation or fever.

3. Specific Barrier- It is also known as adaptive immuntiy or acquired immunity. This is a 3rd line of defence which is highly specific to invading pathogens. It is said specific because it target the pathogen. It involves various cells such as, cyto-toxic T-cells, helper T-cells, B-cells that produces antibodies. It involves antigen presenting cells such as dendritic cells, B-cells, etc. that process the pathogen by various antigen-presenting pathways (endogenous and exogenous pathways) and present them to T-cells along with the MHC molecules. However, B-cells does not require processed pathogen and their only work is to secrete specific antibodies against the specific pathogen.