Signal Regulatory Protein Molecules Are Differentially Expressed by CD8− Dendritic Cells

Abstract

A normalized subtracted gene expression library was generated from freshly isolated mouse dendritic cells (DC) of all subtypes, then used to construct cDNA microarrays. The gene expression profiles of the three splenic conventional DC (cDC) subsets were compared by microarray hybridization and two genes encoding signal regulatory protein β (Sirpβ1 and Sirpβ4) molecules were identified as differentially expressed in CD8− cDC. Genomic sequence analysis revealed a third Sirpβ member localized in the same gene cluster. These Sirpβ genes encode cell surface molecules containing extracellular Ig domains and short intracytoplasmic domains that have a charged amino acid in the transmembrane region which can potentially interact with ITAM-bearing molecules to mediate signaling. Indeed, we demonstrated interactions between Sirpβ1 and β2 with the ITAM-bearing signaling molecule Dap12. Real-time PCR analysis showed that all three Sirpβ genes were expressed by CD8− cDC, but not by CD8+ cDC or plasmacytoid pre-DC. The related Sirpα gene showed a similar expression profile on cDC subtypes but was also expressed by plasmacytoid pre-DC. The differential expression of Sirpα and Sirpβ1 molecules on DC was confirmed by staining with mAbs, including a new mAb recognizing Sirpβ1. Cross-linking of Sirpβ1 on DC resulted in a reduction in phagocytosis of Leishmania major parasites, but did not affect phagocytosis of latex beads, perhaps indicating that the regulation of phagocytosis by Sirpβ1 is a ligand-dependent interaction. Thus, we postulate that the differential expression of these molecules may confer the ability to regulate the phagocytosis of particular ligands to CD8− cDC.

The equivalents of human blood and spleen dendritic cell subtypes can be generated in vitro from human CD34+ stem cells in the presence of fms-like tyrosine kinase 3 ligand and thrombopoietin

“…In the mouse and human systems, the cDC subsets can be distinguished on the basis of CD11b and SIRPa expression. 29,30 In vitro, the CD1b/c 1 cDCs expressed high levels of CD11b and SIRPa, while the CLEC9A 1 cDC expressed low levels of CD11b and SIRPa (Figure 1d), similar to their in vivo counterparts. 29,30 Unlike their in vivo counterparts, the CD123 1 pDCs did not express CD304 (BDCA4) and the CLEC9A 1 cDCs did not express CD141 (BDCA3) (data not shown).…”

“…29,30 In vitro, the CD1b/c 1 cDCs expressed high levels of CD11b and SIRPa, while the CLEC9A 1 cDC expressed low levels of CD11b and SIRPa (Figure 1d), similar to their in vivo counterparts. 29,30 Unlike their in vivo counterparts, the CD123 1 pDCs did not express CD304 (BDCA4) and the CLEC9A 1 cDCs did not express CD141 (BDCA3) (data not shown). However, it has recently been shown that the CD8 1 cDCs in mouse and the BDCA3 1 cDCs in human blood uniquely express XCR1.…”

“…A number of molecules have been shown to be differentially expressed by the murine cDC subsets including CD8, Sirpa, CD11b, Clec9A and CD24. These markers have been used to segregate DC subsets in the spleen, 30,42 the thymus 30,42 and in Flt3L cultures in vitro. 7 Murine DC subsets also have unique developmental origins and specialized functions reflected in the differential expression of and requirement for transcription factors, [33][34][35] expression of TLRs 7,36,37 and production of cytokines.…”

Dendritic cells in the thymus contribute to T-regulatory cell induction

“…The plasmacytoid dendritic cell (pDC) and two conventional dendritic cell (cDC) subsets defined based on CD8␣ and Sirp␣ expression: the CD8 lo Sirp␣ hi/ϩ cDCs (Ϸ30% of cDCs, Sirp␣ ϩ TcDCs hereafter) and the CD8 hi Sirp␣ lo/Ϫ cDCs (Ϸ70% of cDCs, Sirp␣ Ϫ TcDCs hereafter) (20,21). Sirp␣ Ϫ TcDCs develop from intrathymic lymphoid precursors (22,23).…”

Comparable T helper 1 (Th1) and CD8 T-cell immunity by targeting HIV gag p24 to CD8 dendritic cells within antibodies to Langerin, DEC205, and Clec9A

“…Three of the major DC subsets in mouse secondary lymphoid organs are as follows: (i) CD11c high CD8 − DCs, (ii) CD11c high CD8 + DCs, and (iii) CD11c int CD45RA + Gr1 + plasmacytoid DCs (PDCs) (12). For example, when CD8 − DCs take up antigen, they more efficiently form MHC II complexes (13) and elicit T cells producing IFN-γ and IL-4 (14,15).…”