The expression of CD21 in human B-cell lymphomas is variable (Nadler et al, 1983; Echeverri et al, 2002), most likely in part because it is the receptor for Epstein–Barr virus (EBV), as infection with this virus induces high expression of CD21 (CR2) and its co-receptor CD35 (CR1; Freeman et al, 1982; Cohen et al, 1987). The gene discussed is CR1; the disease is infection.