Cellular immunity in infectious mononucleosis: I. Spontaneous and phytohaemagglutinin-induced blast transformation in infectious mononucleosis, with special reference to depressed cellular reactivity and stimulation-blocking serum factors.

Lymphocytes of patients with infectious mononucleosis (IM), EBV sero-positive subjects, patients with viral infections other than EBV, and EBV sero-negative subjects were tested for phytohaemagglutinin (PHA)-induced and spontaneous transformation in vitro. Lymphocytes of EBV sero-positive healthy subjects, tested in autologous serum, have higher spontaneous transformation than those of EBV sero-negative subjects. IM patients, in the acute phase of illness, have depressed spontaneous lymphocyte transformation, independent of serum factors. Serum factors are present in acute IM that depress spontaneous transformation further, and to a lesser extent depress reactivity to PHA. By the time the IM patients had recovered, greater than 9 weeks after onset of illness, the defects observed had disappeared.