Role of tumor necrosis factor in Listeria resistance of nude mice.

The effects of sheep anti-murine recombinant tumor necrosis factor-alpha (TNF-alpha) on resistance to Listeria monocytogenes infection were studied in T cell-deficient nu/nu mice. The sheep anti-TNF-alpha antibody preparation was specific for TNF since it neutralized 300 U of recombinant murine TNF-alpha in vitro at a dilution of up to 1/1,000 but did not neutralize 32 U of interferon (IFN)-alpha, -beta or 32 U of IFN-gamma in vitro at a 1/20 dilution. When tested in vivo in sublethally Listeria-infected nu/nu or T cell-competent C57BL/6 or ICR mice, a single treatment of 0.2 ml anti-TNF-alpha given intraperitoneally on either day -1,0 or +1 resulted in the death of mice by day 5-7 due to the uncontrolled growth of Listeria; bacterial counts in spleen and liver were increased on days 3-5 by a factor of 10-1,000 in these organs. When examined histologically, organs from mice with the anti-TNF-alpha treatment contained more, and considerably bigger, lesions that exhibited central necrosis. The enhancing effect of anti-TNF-alpha on Listeria infection seemed greater early during Listeria infection on days 1-6 when compared to later phases of the infection around days 6-10. From the data presented we conclude that in addition to other lymphokines, such as IFN-gamma, TNF-alpha is of importance during the entire course of a Listeria infection in nu/nu mice.