 This is a key step in the production of high affinity antibodies as B cells and T cells need to interact in order to activate the Ig class switch.CXCR5 has been shown to be expressed on both CD4 and CD8 T cells, though it is often regarded as the defining marker for T Follicular Helper (Tfh) cells.Recently, it was shown that CXCR5 overexpression in breast cancer patients highly correlates with lymph node metastases, and elevated CXCR5 expression may contribute to abnormal cell survival and migration in breast tumors that lack functional p53 protein.