Is CR2 a T cell co-receptor?

CR2, or Complement Receptor 2, is not a T cell co-receptor. Instead, it primarily serves as a receptor for complement component C3d and is predominantly expressed on B cells. Its main role is to enhance B cell activation and proliferation in response to antigen recognition. CR2 is part of the signaling complex that helps B cells to respond more vigorously to antigens, particularly when those antigens are opsonized with complement proteins.

In contrast, T cell co-receptors, such as CD4 and CD8, facilitate T cell activation by aiding in the recognition of peptide-MHC complexes on antigen-presenting cells. Thus, indicating that CR2's function and expression are specific to B cells rather than T cells helps clarify why this answer is correct. Overall, the assertion that CR2 is a T cell co-receptor is incorrect, leading to the conclusion that the statement is false.