Interferon induces peripheral lymphadenopathy in mice.

Inoculation (i.p. or i.v.) of partially purified or highly purified (H.P.) mouse interferon (electrophoretically pure in SDS-PAGE gels) into different strains of mice (C3H, BALB/c, Swiss, heterozygote and athymic nu/nu C57BL/6) results in a marked increase in the weight and in the total number of cells in axillary and inguinal lymph nodes. Interferon injected into the hind footpad induced an increase in the weight of the ipsilateral popliteal lymph node compared with the contralateral lymph node. Inoculation of noninterferon proteins (impurities) obtained in the course of purification of this H.P. interferon, mock interferon, or human leukocyte interferon were without effect. Experiments were undertaken to elucidate the mechanism by which interferon induced an increase in the weight (number of cells) of peripheral lymph nodes. There was no evidence that the afflux of transferred chromium-labeled lymphoid cells to lymphoid tissue was increased in interferon-treated recipient mice. There was no evidence that interferon treatment resulted in a stimulation of the multiplication of cells within the peripheral lymph nodes. Since we observed a decrease in the number of lymphocytes in the thoracic duct lymph and in the peripheal blood of interferon-treated mice, we suggest that interferon treatment resulted in an inhibition of egress of lymphocytes from lymphoid tissue. The finding that interferon treatment of mice alters patterns of lymphocyte circulation may be relevant to some of the effects of interferon on the immune system and may explain in part the lymphadenopathy observed in the course of some viral infections.