Isoprinosine abolishes the blocking factor-mediated inhibition of lymphocyte responses to Epstein-Barr virus antigens and phytohemagglutinin.

Acute infectious mononucleosis (IM) is accompanied by measurable abnormalities of immune function, including a transient immunosuppression. The sera of patients with acute IM contain an IgG blocking factor which binds to T-lymphocytes and decreases their responses to antigens and mitogens. The experiments reported herein indicate that isoprinosine, an immunopotentiating agent, can reverse this inhibition of T cells by IM-associated IgG blocking factor. Isoprinosine may be a useful tool in understanding the interactions between blocking factors and lymphocytes; moreover, isoprinosine may be of value in patients with abnormal clinical responses to Epstein-Barr virus (EBV) such as chronic IM or persistent active EBV infections.