Cytokines represent a diverse group of soluble proteins that play a key role in a number of physiological processes, including regulation of both the innate and adaptive immune responses. Cytokines are generally secreted in small amounts, and are relatively unstable. Therefore, detection and measurement of cytokine local concentrations in a tissue extracellular matrix can be challenging. To investigate cytokines involved in cancer prevention by tumour-specific CD4+ T cells, we have developed a strategy consisting of embedding subcutaneously injected tumour cells in a collagen gel (Matrigel) . Matrigel is a soluble basement membrane isolated from the Engelbreth-Holm-Swan (EHS) tumour . This extract resembles the complex extracellular environment found in many tissues. The Matrigel is liquid at 4°C but when incubated at room temperature, the Matrigel proteins self-assemble forming a gel plug. In short, the Matrigel functions as an extracellular matrix in which infiltrating immune cells  and secreted cytokines can be analyzed at various time points after s.c. injections .