CXCR5 and systemic lupus erythematosus: CD8 contributes apparently to the immune response, T cell activation, and regulation of the immune response, etc. The elevated levels of ICOS and CXCR5 on CD8 T cells from SLE patients suggest a pathogenic CD8 T cell subset exhibiting amplified cytotoxicity and potentially facilitating a stronger antibody response through B cell activation [58].