Resident lung antigen-presenting cells have the capacity to promote Th2 T cell differentiation in situ

Antigen exposure via airway epithelia is often associated with a failure to prime or with the preferential priming of Th2 cells.We previously reported that the intranasal delivery of a Th1-inducing antigen promoted Th2-dominated responses, rather than the expected Th1 responses.Thus, we proposed that when pulmonary T cell priming is induced, the lung microenvironment might intrinsically favor the generation of Th2 types of responses.To establish a potential mechanism for such preferential priming, we examined the initial interactions between antigens and resident antigen-presenting cells (APCs) within the lung.We show that intranasally delivered antigens are preferentially taken up and can be presented to antigen-specific T cells by a resident population of CD11c bright APCs.Most of these antigen-loaded APCs remained within lung tissues, and migration into secondary lymphoid organs was not crucial for T cell priming to occur within the pulmonary tract.Furthermore, these pulmonary APCs demonstrated a marked expression of IL-6 and IL-10 within hours of antigen uptake, suggesting that resident tissue APCs have the capacity to promote Th2 T cell differentiation in situ.