Immune discrimination of the environmental spectrum through C-type lectin receptors

Our bodies are continuously assaulted by infection and tissue damage; most of these injurious insults are primarily sensed by immune receptors to maintain tissue homeostasis. Although immune recognition of proteins or nucleic acids has been well characterized, the molecular mechanisms by which immune receptors discriminate lipids to elicit suitable immune responses remain elusive. Recent studies have demonstrated that the C-type lectin receptor family functions as immune sensors for adjuvant lipids derived from pathogens and damaged tissues, thereby promoting innate/acquired immunity. In this review, we will discuss how these receptors recognize lipid components to initiate appropriate, but sometimes deleterious, immune responses against environmental stimuli. We will also discuss an aspect of inhibitory C-type lectin receptors; their ligands might reflect normal self which silences the immune response regarded as "silence"-associated molecular patterns or may be associated with escape strategies of pathogens as "evasion"-associated molecular patterns.