C-type lectin-like receptors on myeloid cells

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Host defense against pathogens involves recognizing pathogen-associated molecular patterns (PAMPs) via pattern recognition receptors (PRRs), including toll-like receptors (TLRs) and C-type lectins.
• Non-classical C-type lectins were traditionally associated with natural killer (NK) and T cells, but are increasingly found on myeloid cells.
• While NK cell C-type lectins regulate activation via MHC class I recognition, myeloid-expressed counterparts exhibit broader functions and ligands.

Purpose of the Study:

• To review the emerging roles of non-classical C-type lectins expressed on myeloid cells.
• To highlight the diverse functions and potential ligands of these myeloid-expressed C-type lectins.
• To discuss their prospective contributions to innate and adaptive immunity.

Main Methods:

• Literature review of studies identifying and characterizing myeloid-expressed C-type lectins.
• Analysis of known and potential signaling motifs within C-type lectin-like molecules.
• Examination of gene clustering for potential receptor/ligand pairs.

Main Results:

• A growing number of non-classical C-type lectins are identified on human and mouse myeloid cells.
• These receptors possess diverse functions and ligands, distinct from their NK cell counterparts.
• Some C-type lectin-like molecules have activating/inhibitory motifs regulating granulocyte and monocyte functions.
• Natural ligands for most myeloid C-type lectins remain unidentified, complicating functional definition.
• Some C-type lectin-like lectins encoded by the same gene cluster may act as receptor/ligand pairs.

Conclusions:

• Myeloid-expressed C-type lectins represent a significant, yet underexplored, component of the immune system.
• Further research is needed to identify natural ligands and elucidate the precise roles of these receptors in health and disease.
• These receptors hold prospective importance in regulating myeloid cell function and interactions with other immune cells, impacting innate and adaptive immunity.