Question

Various types of damage can lead to acute inflammation, including cuts and abrasions, heat, and microbial damge. Some microbes have structures which can trigger the acute inflammatory repsonse when they invade tissues.
What structural characteristics common to Gram-negative bacteria may trigger the acture inflammatoty respone?

A. Teichoic acid
B. Mycolic acid
C. Lipid A
D. External polysaccharides

Answer 1

Answer:

C: Lipid A

Explanation:

Lipid A is a component of the endotoxin (also called the lipopolysaccharide)  present in Gram-negative bacteria. The LPS has 3 component namely;

• the O-antigen: they are antigenic determinants and are the outer carbohydrate chains
• the core polysaccharide: forms the centre core of the LPS
• The Lipid A: forms the innermost part of the LPS and triggers acute inflammatory responses (e.g endotoxic shock) when released.

Upon detection of an endotoxin which forms the component of the outer membrane of a Gram negative organism (in exception to the Gram-positive bacteria called Listeria monocytogenes), the innate immune defense system (e.g macrophages and T-helper cells) are alerted to initiate elimination strategies towards the invading organism. Lipid A binds to the CD14/MD2 receptor on macrophages and monocytes which activates the nuclear factor kappa- light chain enhancer (NF-κβ). The activation of NF-κβ protein triggers the production of inflammatory cytokines which includes Interleukin-1 (IL-1), IL-12, IL-18 as well as the Tumor necrosis factor- alpha (TNF-α).

Inflammatory responses are as a result of the release of these cytokines which sometimes leads to shock and death of the host