Tonsillar CD56brightNKG2A+ NK cells restrict primary Epstein-Barr virus infection in B cells via IFN-γ

Natural killer (NK) cells constitute the first line of defense against viruses and cancers cells. Epstein-Barr virus (EBV) was the first human virus to be directly implicated in carcinogenesis, and EBV infection is associated with a broad spectrum of B cell lymphomas. How NK cells restrict EBV-associated oncogenesis is not understood. Here, we investigated the efficacies and mechanisms of distinct NK cell subsets from tonsils, the portal of entry of EBV, in limiting EBV infection in naive, germinal center-associated and memory B cells. We found that CD56(bright) and NKG2A expression sufficiently characterizes the potent anti-EBV capacity of tonsillar NK cells. We observed restriction of EBV infection in B cells as early as 18 hours after infection. The restriction was most efficient in naive B cells and germinal center-associated B cells, the B cell subsets that exhibited highest susceptibility to EBV infection in vitro. IFN-gamma release by and partially NKp44 engagement of CD56(bright) and NKG2A positive NK cells mediated the restriction that eventually inhibited B-cell transformation. Thus, harnessing CD56(bright)NKG2A(+) NK cell function might be promising to improve treatment strategies that target EBV-associated B cell lymphomas.