Final answer:
TLR4 is a toll-like receptor found on the cell membrane of immune cells with a critical role in innate immunity. The statement that TLR4 does not contain a cytoplasmic TIR domain is false, as the TIR domain is instrumental for signal transduction following pathogen detection.
Step-by-step explanation:
The subject at hand is related to the immune system, specifically to a protein called toll-like receptor 4 (TLR4), which is a member of the TLR family involved in pathogen recognition and activation of innate immunity. It is crucial to understand that TLR4 is indeed present on the cell membrane of immune cells, where it plays a critical role in detecting lipopolysaccharides (LPS) from Gram-negative bacteria as part of the immune response. The extracellular domain of TLR4 is where it associates with LPS and co-receptors, leading to the transduction of signals which ultimately result in an immune response.
Contrary to one of the statements provided, TLR4 does contain a cytoplasmic TIR domain, which is essential for signal transduction following the recognition of pathogenic molecules. The TIR domain is responsible for interacting with downstream adapter proteins, leading to the activation of NF-κB and the production of pro-inflammatory cytokines. This interaction is a characteristic feature of TLRs that differentiates them from other types of receptors, such as T-cell receptors (TCRs) which function distinctly at the adaptive level of the immune response.
Therefore, the statement 'TLR4 does not contain a cytoplasmic TIR domain' is false. Understanding the structure and function of TLR4 is important in immunology and can have implications for developing treatments for various diseases, including infectious, inflammatory, and autoimmune conditions.