Infectious mononucleosis: sequential immunologic, cytochemical, and cytokinetic studies on single lymphoid cells in peripheral blood.

Sequential immunologic, cytochemical, and cytokinetic studies were done on single lymphoid cells in the peripheral blood of 6 children with infectious mononucleosis (IM) and 1 child with toxoplasmosis 1-2 wk after onset of symptomatology. The absolute number of AET-SRBC rosetting (E+) cells was increased in all patients; the absolute number of cells with surface IgM (slgM+) was increased in 3 of 7 patients. On the average, 46% of all lymphoid cells were E+la+slgM-, 35% E+la-slgM-, and 5% E-la+slgM+. Of the E+la+slgM- cells, only 7% were shown to have a dot-like esterase reaction pattern. Of the E+la-slgM-cells, 17% were esterase positive. The mean labeling index of the former was 18.2%, the mean labeling index of the latter 4.4%. No proliferating slgM+ cells were observed in the 6 children with IM. The esterase reactions and the labeling indices of suppressor-cytotoxic and inducer-helper T cells were similar to those of E+la+slgM- and E+la-slgM- cells, respectively. These results suggest that the vast majority of the atypical cells in IM corresponds to activated suppressor cells, while a minority appears to be proliferating helper cells.