Principles of MAT

A minor sub-population of human PBMC consist of monocytes, elite members of the innate immune system. The function of these cells is to recognize common features of ^ ^ foreign ^ ^ relying on their pattern recognition receptors, also called or toll like receptors (TLRs). In the absence of TLR stimulation, monocytes are in a resting state and do not secret cytokine (illustrated in the figure as the blue cells). Each batch of MAT PBMC offerd by CTL-MAT is thoroughly screened for containing resting monocytes only, thus producing a low cytokine background for the CTL MAT Kit.

If a test substance is contaminated with microbial products, these will bind to TLRs on monocytes, resulting in the activation of these cells. If LPS is present, it will bind to TLR4, LTA ( a constituent of Gram positive bacteria), peptidoglycan (PGN, a constituent of most bacteria), or Zymosan (a constituent of yeast) will bind to TLR2, leading to monocyte activation. As MAT tests sensitively detect microbial contaminants in test substances, we made sure that all constituents of the CTL MAT Kit are void of such, thus producing a low cytokine background for the CTL MAT Kit.

Upon TLR engagement in the presence of microbial antigens (contaminations), monocytes become activated (shown in the figure as red cells) and start secreting cytokines including interleukin 6 (IL-6), the primary inducer of the fever reaction in vivo. It takes monocytes approximately 20 h to reach peak level of IL-6 production. To allow for it, the PBMC are cultures with the test substance for 20 h before IL-6 is measured in the superna- tant.For successful MAT assays, therefore, PBMC donors need to be selected who are particularly proficient in IL-6 production. Moreover, the PBMC need to be cryopreserved in a way so they retain their full viability and functionality in spite of the cryopreservation. Each batch of PBMC included as indicator cells in CTL-MAT kits has been carefully selected for unimpaired IL-6 production upon thawing.