Description
Histamine (1H-imidazole 4-ethaneamine) is a biogenic amine known to play a key role in immediate hypersensitivity and inflammation reactions, as well as in several atopic diseases. As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues. Bacterial decarboxylation of the amino acid histidine in fresh fish produces histamine, which can be used as a health hazard biomarker indicative of bacterial contamination. The histamine kit accurately measures histamine from PBMCs and cell-based formats.
HTRF assays offer many advantages over other technologies:
Homogeneous add-and-read format
No wash steps
Low background
Straightforward miniaturization from 96- or 384-well microplates to high density assay formats such as 384-well low volume and 1536-well plates
Stable signal, providing flexibility in time of readout or size of assays
Assay principle
The kit is based on a competitive format involving a specific antibody labelled with Cryptate (donor) and histamine coupled to d2 (acceptor). Histamine produced by cells competes with d2-labelled histamine for binding to monoclonal anti-histamine Eu Cryptate.
Assay protocol
The histamine assay features a streamlined protocol with only two incubation steps: - Sample with acylation buffer and acylation reagent - Histamine detection using HTRF reagents. This protocol requires a single, three-hour incubation period following the acylation step.
Histamine detection upon allergen stimulation
Four independent blood samples (Donor A to D) were used to measure the spontaneous release of histamine, as well as upon stimulation with 5 allergen mixes including 6 grass mix, house dust mite, cat epithelium, inhalant mix and common ragweed allergen. *The anti IgE antibody (Ref # MABETS07) used as a positive control in the experiment can be purchased separately
Histamine detection upon REBL-2H3 stimulation
Rat basophils (RBL-2H3) were cultured in the presence or absence of 2.5 µM ionomycin to stimulate histamine release. Total histamine content was determined by lysing cells and spontaneous release was evaluated by incubating the cells in medium only. Histamine detection was performed following 30 minute cell stimulation at 37 ºC using the standard HTRF histamine assay protocol.
Histamine detection upon PBMC stimulation
Similar studies were performed using human peripheral blood basophils from two individual donors. Non-specific release of histamine using Ionomycin was compared to specific degranulation induced by cross-linking a membrane-bound IgE receptor with anti-IgE. Histamine detection was performed using the standard HTRF histamine assay protocol following 30 minutes of stimulation of peripheral blood basophils at 37ºC. Error bars represent a standard deviation of 3 replicates.
