CR receptors, also known as complement receptor, refer to a group of proteins found on the surface of various immune cells, particularly white blood cells, that are involved in the recognition and binding of complement proteins. Complement receptors play a crucial role in the immune response and the clearance of pathogens, as they mediate the opsonization process, phagocytosis, and the initiation of inflammatory responses.
The CR receptor family consists of several distinct types of receptors, including CR1, CR2, CR3, and CR4, each with its unique functions and distributions. CR1, also known as CD35, is widely expressed on various immune cells, such as macrophages and neutrophils, where it enhances the uptake of complement-opsonized particles and pathogens. CR2, or CD21, is mainly found on B cells, where it forms a complex with CD19 and CD81, facilitating the activation of B cells upon recognition of complement-coated antigens.
CR3 and CR4, also known as CD11b/CD18 and CD11c/CD18, respectively, are primarily expressed on phagocytes, such as monocytes, macrophages, and neutrophils. These receptors play a crucial role in the adhesion of phagocytes to complement-coated surfaces and the subsequent engulfment and destruction of pathogens. Furthermore, CR3 and CR4 are involved in signal transduction processes that lead to the release of pro-inflammatory molecules, contributing to the initiation and progression of immune responses.
Overall, CR receptors are essential components of the immune system, playing a vital role in the recognition, opsonization, phagocytosis, and regulation of inflammatory responses mediated by the complement system.
