What substances can CR3 and CR4 bind to?

CR3 and CR4 are receptors that belong to the integrin family and are primarily involved in the immune response. These receptors are known to bind to specific ligands on pathogens or immune complexes.

The correct answer highlights that CR3 and CR4 can bind to IC3b, which is an opsonized form of the complement component C3b, and also to LPS (lipopolysaccharides), which are components of the outer membrane of Gram-negative bacteria. The binding of CR3 and CR4 to these ligands plays a crucial role in phagocytosis and in the activation of immune responses, as it facilitates the recognition and clearance of pathogens.

In the context of immune signaling, this interaction enhances the ability of immune cells, particularly phagocytes, to engulf and destroy pathogens, ultimately contributing to the overall function of the innate immune system. The interaction between these receptors and their ligands underscores the critical role of complement proteins in mediating immune responses.

Understanding the specific ligands that CR3 and CR4 interact with helps clarify their functional significance in health and disease, especially concerning infections and immune deficiencies.