在 FLT3 配体骨髓培养中，从表达高水平 MHC II 类分子的 CD11c(+) 细胞中鉴定树突状细胞前体

Dendritic cells (DCs) are readily generated from the culture of mouse bone marrow (BM) treated with either granulocyte macrophage-colony stimulating factor (GM-CSF) or FMS-like tyrosine kinase 3 ligand (FLT3L). CD11c + MHCII + or CD11c + MHCII hi cells are routinely isolated from those BM cultures and generally used as in vitro -generated DCs for a variety of experiments and therapies.

Here, we examined CD11c + cells in the BM culture with GM-CSF or FLT3L by staining with a monoclonal antibody 2A1 that is known to recognize mature or activated DCs. Most of the cells within the CD11c + MHCII hi DC gate were 2A1 + in the BM culture with GM-CSF (GM-BM culture). In the BM culture with FLT3L (FL-BM culture), almost of all the CD11c + MHCII hi cells were within the classical DC2 (cDC2) gate. The analysis of FL-BM culture revealed that a majority of cDC2-gated CD11c + MHCII hi cells exhibited a 2A1 - CD83 - CD115 + CX 3 CR1 + phenotype, and the others consisted of 2A1 + CD83 + CD115 - CX 3 CR1 - and 2A1 - CD83 - CD115 - CX 3 CR1 - cells. According to the antigen uptake and presentation, morphologies, and gene expression profiles, 2A1 - CD83 - CD115 - CX 3 CR1 - cells were immature cDC2s and 2A1 + CD83 + CD115 - CX 3 CR1 - cells were mature cDC2s.

Unexpectedly, however, 2A1 - CD83 - CD115 + CX 3 CR1 + cells, the most abundant cDC2-gated MHCII hi cell subset in FL-BM culture, were non-DCs. Adoptive cell transfer experiments in the FL-BM culture confirmed that the cDC2-gated MHCII hi non-DCs were precursors to cDC2s, i. e. , MHCII hi pre-cDC2s. MHCII hi pre-cDC2s also expressed the higher level of DC-specific transcription factor Zbtb46 as similarly as immature cDC2s.

Besides, MHCII hi pre-cDC2s were generated only from pre-cDCs and common DC progenitor (CDP) cells but not from monocytes and common monocyte progenitor (cMoP) cells, verifying that MHCII hi pre-cDC2s are close lineage to cDCs. All in all, our study identified and characterized a new cDC precursor, exhibiting a CD11c + MHCII hi CD115 + CX 3 CR1 + phenotype, in FL-BM culture.