Monocyte Activation Test (MAT)
The Monocyte Activation Test, or MAT, has been in development since 1995 72. The test involves using monocytes in human blood to test for a reaction to endotoxins. The human blood is exposed directly to the test surface or test therapeutic and the pro-inflammatory cytokine IL-1β is measured. The cytokine release is measured by enzyme-linked immunosorbent assay (ELISA) 73,74. The ELISA is used by attaching a protein complex, usually antibodies designed to trap the IL-1β released by the monocytes and an enzyme that will release a colored substrate when the cytokine binds to the complex, to the walls of a vessel, then adding the blood from the MAT 75. If the cytokines are present, they will bind to the protein complex, releasing the colored substrate that can either be detected by the naked eye or by spectrometers, similar to a chromogenic LAL test 49. The test also has the added benefit of testing all pyrogens and inflammatory materials that would prove harmful to human patients 76,77. It avoids animal testing and has a detection of limit of as little as 10 pg/ml of endotoxin solution, and conveniently, this limit becomes even smaller, and the test becomes more accurate when using cryogenically-preserved human blood. This aids in storage and transportation of the human blood for testing if the blood can be cooled and preserved without sacrificing accuracy 73,78,79. The monocytes can be prepared in a variety of ways. Some experiments have used whole human blood, while others use monocytes harvested from leukocyte filters at blood donation centers 78. This method displays high precision by being able to detect non-endotoxic pyrogens and their effect on possible patients of the tested material. However, as there is often a limited supply of human blood to be used for simply testing, inconsistencies can arise when using large quantities of blood are used 72,80.