This chapter is divided into two sections, the first dealing with a novel immune activation gene, denoted
Act
-2. This gene encodes a secreted protein that may represent a new cytokine. The Act-2 protein shares significant homology with proteins in two related families of small secreted proteins. Act-2 is rapidly synthesized by activated T cells, B cells and monocytes. The second section deals with interleukin-2 receptors. These receptors are now known to be comprised of three distinct classes of receptors, formed by various combinations of two IL-2 binding proteins, the α and β chains. The low-affinity receptors contain α, but not β chains; the intermediate-affinity receptors contain β, but not α chains, and the high-affinity receptors contain both α and β chains. The β chain appears to be tyrosine phosphorylated. We discuss evidence for the existence of another protein of relative molecular mass 100 000, which appears to be a subunit of at least the high-affinity receptor.
Frizzled-5: a high affinity receptor for secreted frizzled-related protein-2 activation of nuclear factor of activated T-cells c3 signaling to promote angiogenesis
