Which component commonly remains on red blood cells after cleavage of C3b?

After the cleavage of C3b, the component that commonly remains attached to red blood cells is C3d. This process occurs during the complement activation pathway, where C3b is cleaved into smaller fragments, including C3d.

C3b acts as an opsonin, marking pathogens for destruction and facilitating their clearance from the circulation. When C3b is cleaved, it reduces in size and forms C3d, which continues to retain its ability to bind to complement receptors, playing a significant role in enhancing immune responses. C3d, in particular, binds to complement receptor 2 (CR2) on B cells, which can lead to B cell activation and proliferation.

Understanding this fragment's role is crucial, especially in the context of blood banking and immunohematology, as the presence of C3d on the surface of RBCs can influence their interaction with the immune system. This knowledge is particularly relevant when considering the identification of antibody-mediated hemolytic events or in scenarios such as sensitization testing.

Other components like C3 and various other complement proteins do not typically remain attached in the same way C3d does after the cleavage of C3b, reinforcing the significance of C3d in this context.