Recruitment and in situ renewal regulate rapid accumulation of CD11c+ cells in the lung following intranasal superantigen challenge.

Background: Staphylococcusaureus, a primary source of bacterial superantigen, is known to colonize the human respiratory tract and has been implicated in airway inflammation. The potential pathological effect of staphylococcal enterotoxins on the respiratory tract necessitates a detailed understanding of how they regulate innate immune cells, particularly CD11c-expressing dendritic cells (DCs).
Methods: C57BL/6 mice were challenged intranasally with staphylococcal enterotoxin A (SEA) and at indicated time points lung tissue was perfused, digested and analyzed for CD11c+ expressing cells.
Results: The pulmonary CD11c+ cells can be divided into two major populations based on their MHC II expression. One day following intranasal SEA challenge, there was rapid accumulation of CD11c+ cells expressing medium to high levels of MHC II. The peak accumulation of CD11c+ MHC II- population was observed 2 days after SEA challenge; however, careful examination of this cell population revealed that they were heterogeneous, being comprised of cells bearing CD3, CD19, NK1.1 and F4/80 along with varying levels of CD11c. Nevertheless, there was a 2-fold increase of CD11c+ MHC II- (CD3- CD19- NK1.1- F4/80-) cells in the lungs.
Conclusion: The mechanism of increase in the CD11c+ MHC II- immune progenitor population was mainly due to cellular division rather than migration from blood to lung. In contrast, the early and rapid accumulation of CD11c+ MHC II(hi) cells, conventionally known as DCs, in the lung on day 1 was mostly due to migration from blood. Thus this study examines the pulmonary innate immune response to a powerful immune stimulus.
(Copyright 2008 S. Karger AG, Basel.)