Distinct behavior of myelomonocytic cells and CD8 T cells underlies the hepatic response to Listeria monocytogenes [version 1; referees: 2 approved]

Background: The immune response to Listeria monocytogenes (LM) is characterized by formation of leukocyte rich foci of infection in liver and spleen. Although much has been gained in our understanding of immune response through the study of LM, little is known about spatio-temporal regulation of immune response to Listeria in liver. Methods: We utilize a combination of molecular, genetic and intravital microscopic approaches to gain insight into the dynamics of foci and leukocyte behavior during hepatic Listeriosis. Results: LM foci efficiently exclude blood flow, indicating the presence of a barrier separating the foci and healthy tissue. Despite this barrier, sinusoidal myelomonocytic cells readily enter or transiently interact with cells at the edge of foci of infection. Next, utilizing L9.6 transgenic CD8+ T cells specific for an endogenously processed LM antigen, p60 217-225, along with LM deficient in this epitope, we define the role of TCR in T cell migratory behavior in infected liver. Surprisingly, T cell behavior varies with micro-anatomic locale. Near foci, non-specific adhesion mechanisms dominate lymphocyte behavior. Antigen specific effects on motility became detectable only distal to foci. Conclusions: These data suggest that LM antigens act in a paracrine manner to mediate protection from Listeriosis in the liver