Taken together, this data shows that (1) IL-21 treatment promotes the establishment of KSHV infection in human tonsil B lymphocytes (2) KSHV and IL-21 synergistically promote increased plasma cell frequencies at 3 dpi and (3) both plasma cell frequencies increased plasma cell infection at 3 dpi significantly correlate with the IL-21-mediated increase in total KSHV infection. This evidence concerns the gene IL21 and infection.