Responsiveness to anaphylatoxin C5a delineates hematopoietic lineage of pulmonary dendritic cells (HYP6P.257)

Abstract

Abstract The complement subunit, C5a (anaphylatoxin), can either promote or suppress allergic responses through its effects on pulmonary dendritic cells (DCs). However, DCs are heterogeneous, and responsiveness of specific DC subsets to anaphylatoxins has not been well characterized. Two distinct precursors can give rise to DCs, including fms-like tyrosine kinase receptor 3 (FLT3)-dependent preDCs and FLT3-independent monocytes. The integrins CD11b and CD103 are widely used to identify DC subsets in the lung, but CD11bhi DCs are composed of both preDC-derived conventional DCs (cDCs) and monocyte-derived DCs (moDCs), including Ly-6Chi inflammatory DCs and Ly-6CloCD64hi (also CD14hi) resident moDCs. Microarray analysis of FLT3-dependent CD11bhi cDCs and FLT3-independent CD11bhi moDCs revealed that C5aR/CD88 is highly expressed by moDCs. Flow cytometric analysis confirmed that CD88 is displayed on Ly-6Chi inflammatory DCs and CD64hi resident moDCs, but not on CD103+ and CD64lo cDCs. CD88hi lung DCs were FLT3-independent, and adoptively transferred monocytes differentiated exclusively to CD88hi DCs. Calcium-influx analysis of purified lung DCs upon C5a stimulation confirmed that only Ly-6Chi inflammatory DCs and CD64hi moDCs, but not CD103+ DCs and CD64lo cDCs respond to C5a. Our findings demonstrate that CD88 can reliably distinguish moDC from cDCs, and that only moDCs are directly stimulated by anaphylatoxin C5a.