背景资料:The HB5 monoclonal antibody specifically reacts with human CD21, a 145 kDA glycosylated type I integral membrane protein. CD21 is reported to be involved in B cell activation and proliferation. It is expressed on follicular dendritic cells, mature B cells, a subset of T cells, and a subset of epithelial cells. It is the receptor utilized by the Epstein-Barr virus to infect B cells.