In situ hybridization (ISH) involves hybridization of labeled nucleic acid probes with the target mRNA. As cytokines are soluble mediators exported from the cells in which they are produced, ISH is a powerful technique that can be used to identify the exact identity and location of the cells that produce these soluble mediators. The technique of ISH is useful as a tool to locate mRNA species in histological samples of human tissues, in particular human nerve sections (1). Using histological sections of such tissues has several distinct advantages, which complement studies that use extracted nucleic acids. For example, ISH can localize mRNA within single cells, can follow cell development regarding the expression of the target mRNA in embryos, and can be combined with immunohistochemistry (2) to detect the mRNA and the proteins encoded by them.