The only characteristic that designates various classes is their competence to bind mutual ligands. SRs are a structurally heterogeneous superfamily of proteins that belong to different classes with very little or no structural resemblance. Scavenger receptors (SRs) were shown for the first time on macrophages to function in endocytosis and degradation of modified (acetylated) low-density lipoproteins (LDLs). This review majorly gives an insight on the functional aspect of scavenger receptors in host defence and describes their mode of action extensively in various immune pathways involved with each receptor type. Unlike, most of the scavenger receptors discussed below have both membrane and soluble forms that participate in scavenging the role of a potential scavenging receptor Angiotensin-Converting Enzyme-2 has also been discussed whereby only its soluble form might participate in preventing the pathogen entry and replication, unlike its membrane-bound form.

Scavenger receptors are documented as pattern recognition receptors and known to act in coordination with other co-receptors such as Toll-like receptors in generating the immune responses against a repertoire of ligands such as microbial pathogens, non-self, intracellular and modified self-molecules through various diverse mechanisms like adhesion, endocytosis and phagocytosis etc. Numerous scavenger receptors have been discovered so far and are apportioned in various classes (A-L). They are functionally diverse as they are involved in various disorders and biological pathways and their major function in innate immunity and homeostasis. Scavenger receptors belong to a superfamily of proteins that are structurally heterogeneous and encompass the miscellaneous group of transmembrane proteins and soluble secretory extracellular domain.

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