Am. J. Respir. Crit. Care Med., Volume 161, Number 2, February 2000, 535-542

Accumulation of Macrophages with Dendritic Cell Characteristics in the Pulmonary Response to Listeria

RICHARD L. KRADIN, HIDEO SAKAMOTO, FREDERIC I. PREFFER, DAVID DOMBKOWSKI, KIM M. SPRINGER, and CAROL P. LEARY

Departments of Pathology and Medicine, Massachusetts General Hospital, Boston, Massachusetts

Pulmonary immunity reflects a balance between proinflammatory and immunosuppressive factors in the lung. To determine the immune activities of exudate macrophages in the pulmonary immune response, Lewis rats were injected intratracheally with heat-killed Listeria (HKL), labeled ex vivo with the lipophilic dye PKH-26. At 24 h, macrophages from bronchoalveolar lavage fluid were purified on the basis of their surface membrane expression of RMA, a macrophage-specific antigen, which is brightly expressed by resident alveolar macrophages but dimly expressed by monocytes. Pulmonary macrophages were analyzed for uptake of PKH-26-HKL, and RMA^bright/dim macrophages sorted by FACS were compared for cytokine expression, nitric oxide (NO) release, and APC activities. RMA^bright macrophages were OX-62, B7, and factor XIIIa; they were the dominant mediators of phagocytosis when low doses of HKL were administered intratracheally but did not support the proliferation of T lymphocytes. RMA^dim exudate macrophages were OX-62⁺, B7⁺, and factor XIIIa⁺. They expressed more IL-1 and TNF, but less nitric oxide, than did RMA^bright macrophages; they were excellent APCs for T cell responses. We conclude that a subset of RMA^dim exudate macrophages shows phenotypic and functional evidence of dendritic cell differentiation. Kradin RL, Sakamoto H, Preffer FI, Dombkowski D, Springer KM, Leary CP. Accumulation of macrophages with dendritic cell characteristics in the pulmonary response to Listeria.

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