Successful protection against cancer, infectious diseases or autoimmunity is the result of a multitude of cellular interactions within the immune system, including antigen presenting dendritic cells, natural killer cells, antibody forming B-cells and cytotoxic T-cells. Despite detailed molecular information on individual immune cell subtypes, virtually no information is available on the functional capacities of individual immune cell subtypes. Do all cells behave similar, can we distinguish different but specific patterns, or are responses from individual cells totally stochastic? So far both in vivo animal models, as well as in vitro laboratory test tube experiments, only yield a global outcome of interactions of often millions of cells rather than providing insight in the functional contribution of individual immune cells. Recent advances in microfluidic techniques now allow for the first time to perform systematic high throughput immune function analyses of individual cells in a highly controlled manner. In this project, by exploiting this technique, we plan to study well defined homogeneous immune cells for their capacity and plasticity in inducing immune responses. More specifically we will start by studying cytokine secretion by cell lines and thereafter will probe the cytokine profile off various immune cells. Studying immune interactions at this level of individual cells is the only way to unambiguously elucidate what cellular properties correlate with immune protection.