Figure 5 Co‐immunostaining of B19 VP1/VP2 protein (nitroblue tetrazolium, purple black) and CD20 antigen (3‐amino 9‐ethylcarbazole, brown; A, ×100) or CD3 antigen (dimethylaminoazobenzene, brown; B, ×40) in the Rosai–Dorfman disease‐affected lymph node of case 1. Double labelling of B19‐positive cells with CD20 and CD3 antibodies shows the B lymphocyte and T lymphocyte origin of the virus‐infected cells.