Redefining Myeloid Cell Subsets in Murine Spleen

Area of Science:

• Immunology
• Cell Biology
• Hematology

Background:

• The spleen harbors diverse myeloid and dendritic cell (DC) subsets with distinct phenotypes and functions.
• Recent advancements in flow cytometry have improved the characterization of splenic dendritic cell subsets.
• A comprehensive understanding of all splenic myeloid subsets is crucial for identifying novel cell populations.

Purpose of the Study:

• To identify and thoroughly characterize a novel splenic cell subset, termed "L-DC."
• To delineate the phenotypic and developmental distinctions between L-DC and other known splenic myeloid and DC subsets.
• To investigate the relationship of L-DC to conventional DCs and monocytes.

Main Methods:

• Utilized multi-parameter flow cytometry to analyze cell surface phenotypes in murine spleen.
• Defined L-DC by characteristic expression of CD11b, CD11c, MHCII, Ly6C, Ly6G, CD43, Siglec-F, and CD115.
• Analyzed L-DC prevalence in mutant mice and assessed their development independent of BATF3, FLT3L, and GM-CSF.

Main Results:

• L-DC were phenotypically characterized as CD11b(hi)CD11c(lo)MHCII(-)Ly6C(-)Ly6G(-)CD43(+)Siglec-F(-)CD115(-).
• This phenotype clearly distinguished L-DC from conventional DCs and monocytes, including eosinophils.
• Changes in L-DC numbers in mutant mice confirmed their distinctness from cDC and monocyte subsets.
• L-DC development was found to be independent of BATF3, FLT3L, and GM-CSF.

Conclusions:

• L-DC represent a novel, phenotypically distinct subset within the spleen.
• L-DC development occurs independently of key regulatory factors governing conventional DC and monocyte differentiation.
• These findings expand our understanding of splenic myeloid cell heterogeneity and regulation.