
<ArticleTitle>Detection of intracellular phosphorylated <prot>STAT-4</prot> by flow cytometry.</ArticleTitle>
<AbstractText>The convergence of innate and adaptive immunity is critical for host defense, allowing for early protection and the generation of specific responses. <prot>STAT-4</prot> is at that point of convergence, unifying the <prot>IFNalpha</prot> and <prot>IL-12</prot> pathways. Activation of <prot>STAT-4</prot> is crucial to T cell polarization, B cell and NK cell activation, and the control of intracellular pathogens. However, techniques to detect phosphorylated <prot>STAT-4</prot> are cumbersome and require many cells. We have developed a flow cytometric detection technique to investigate <prot>IL-12</prot> signaling in human peripheral blood mononuclear cells. Using different polyclonal antibodies that recognize either total <prot>STAT-4</prot> protein or tyrosine-phosphorylated <prot>STAT-4</prot>, we can easily detect <prot>IL-12</prot> and <prot>IFNalpha</prot> signaling in <prot>PHA</prot>/<prot>IL-2</prot> blasts derived from peripheral blood lymphocytes. This technique not only allows us to evaluate <prot>IL-12</prot> signaling, but it is also less time consuming and labor intensive than alternative methods. Using this flow cytometry-based method, we should be able to detect patients with defects in <prot>IL-12</prot> receptor signal transduction, who typically present with disseminated nontuberculous mycobacterial infections.</AbstractText>
