The biology of circulating B lymphocytes infected with Epstein-Barr virus during infectious mononucleosis.

EBV-infected B cells are present in blood during acute infectious mononucleosis (IM) in surprisingly large numbers. These cells share with cells transformed by EBV in vitro the capacity for unlimited proliferation, but this capacity is quite restricted in the normal host. The unusual extent of plasmacytic differentiation seen in infected cells in vivo early in IM and the loss of this differentiation in the late stages of the disease suggest that these cells are subject to the same immunoregulatory mechanisms that affect normal B cells. The host response to virus-altered B cells is quite complex but is perhaps best viewed as an in vivo autologous mixed lymphocyte reaction initiated by the interaction of T cells with virus-activated B cells.