Highly Increased Natural Killer Cell Number and Lytic Activity in the Murine Peripheral Blood and Lungs after Interferon Induction in Vivo

We have studied the effect of interferon in vivo (induced by polyinosinic-polycytidylic acid (pIC] on the natural killer (NK) cell lytic activity and on the numbers of large granular lymphocytes (LGL) and target-binding cells (TBC) in different lymphoid compartments. One day after the pIC induction the spleen contained two- to four-fold increased lytic activity without a significant change in percentages of TBC and LGL. In the peripheral blood the lytic activity was 12- to 40-fold higher, and a concomitant clear increase in the number of LGL and TBC was seen. In the lungs the increase in lytic activity was 8- to 16-fold and in the number of LGLs ca. 3-fold. These results demonstrate that not only the lytic activity of the pre-existing NK cells but also the total amount of NK cells is clearly elevated in the body, but this could be seen more significantly in other highly NK-active organs than the spleen.