AffinityImmuno Products

Introduction

LILRA3 belongs to the leukocyte immunoglobulin-like receptor family, whose transmembrane members on monocytes, B cells, dendritic cells, and NK cells recognize class I HLA molecules and deliver mostly inhibitory signals. Unlike its relatives, LILRA3 lacks a membrane anchor and is secreted as a soluble protein, allowing it to bind circulating and cell-surface HLA class I molecules, albeit with somewhat lower affinity than membrane-bound family members such as LILRB1 and LILRB2. By occupying these HLA ligands, secreted LILRA3 is thought to compete with membrane-anchored LILRs for the same binding sites, potentially dampening the inhibitory signaling those receptors would otherwise deliver, and it has also been shown to bind monocytes directly and suppress LPS-triggered TNF release. The LILRA3 gene lies within a polymorphic cluster of related receptor genes on chromosome 19, and a common deletion that removes the entire gene is carried by a substantial proportion of the population, making LILRA3 one of the more structurally variable genes in this immune receptor family.

Because a common deletion removes the entire LILRA3 gene in a substantial portion of the population, this assay is particularly useful for immunogenetics research correlating circulating LILRA3 levels with genotype, alongside functional studies of how this soluble decoy competes with membrane-bound LILR family members for HLA class I binding.

Principle of the Assay

This kit uses a sandwich enzyme immunoassay format. The microtiter plate wells are pre-coated with a capture antibody specific to Human LILRA3, which binds the target analyte present in standards or samples added during the first incubation step. A biotin-conjugated detection antibody, also specific to Human LILRA3, is then introduced to bind a second epitope on the captured analyte. Avidin-conjugated horseradish peroxidase (HRP) is subsequently added to each well, linking to the biotin label. Upon addition of TMB substrate solution, a colorimetric signal develops exclusively in wells containing Human LILRA3, the biotin-conjugated detection antibody, and Avidin-HRP. The enzymatic reaction is stopped by the addition of sulphuric acid solution, and absorbance is measured at 450 nm (± 10 nm). Sample concentrations are determined by comparing the optical density of each sample against a standard curve.