NEUTROPHILS ARE ESSENTIAL FOR EARLY ANTI-LISTERIA DEFENSE IN THE LIVER, BUT NOT IN THE SPLEEN OR PERITONEAL-CAVITY, AS REVEALED BY A GRANULOCYTE-DEPLETING MONOCLONAL-ANTIBODY

This study shows that in mice selectively depleted of neutrophils by t reatment with a monoclonal antibody, RB6-8C5, listeriosis is severely exacerbated in the liver, but not in the spleen or peritoneal cavity d uring the crucial first day of infection. At sites of infection in the livers of neutrophil-depleted mice, Listeria monocytogenes grew to la rge numbers inside hepatocytes. By contrast, in the livers of normal m ice neutrophils rapidly accumulated at infectious foci and this was as sociated with the lysis of infected hepatocytes that served to abort i nfection in these permissive cells. In the spleen the situation was di fferent, in that depletion of neutrophils did not result in appreciabl e exacerbation of infection. In this organ intact infected cells, many of which appeared to be fibroblast-like stromal cells, were found at foci of infection in the presence or absence of large numbers of neutr ophils. This suggests that neutrophils are less effective at destroyin g L. monocytogenes-infected target cells in the spleen than in the liv er. Consequently, at least during the first day, the organism remained free to multiply intracellularly in the spleen in cells that are perm issive for its growth. Presumably, the same situation exists in the pe ritoneal cavity, because depleting neutrophils did not severely exacer bate infection initiated at this site.