IHControls™ are comprised of microbeads of 2 different sizes.
IHControls™ Test Microbeads – The larger (test) microbeads, approximately 8 microns in diameter, are coated with portions of HER-2, ER, or PR antigen peptides. The IHControls™ includes microbeads for several different commercial tests, combined together in suspension. Typically, 1/3 – 1/2 of the test microbeads are immunoreactive with any single IHC antibody. The remainder will not stain. They serve as a negative (specificity) control.
IHControls™ Color Standard Microbeads – There are also smaller (3 micron diameter) microbeads that are permanently colored dark brown, regardless of the IHC staining procedure. The small size of these microbeads readily distinguishes them from the larger microbeads. These smaller microbeads serve as a color intensity standard, for comparison during stain intensity scoring of the test microbeads. Color standard microbeads help standardize color intensity measurements regardless of the optical settings.
Figure legend: Unstained (left) and stained (right) IHControls™, 400x magnification. Each image contains unstained test microbeads (bearing an irrelevant antigen/peptide) and smaller dark brown color intensity microbeads. The stained image (right) also contains stained test microbeads.
Visual color intensity estimation – the microbead edge typically appears darker than the center because the edge includes a greater area of stained surface that is tangential to the light path. We recommend evaluating microbead color intensity with a 40x objective lens (400x total magnification).