But the use of immunoglobulin domains is not restricted to the immune system. Since Peter Sonderegger happened to walke into my office when I was working on these slides, I choose some of "his" molecules to illustrate the variety of cell surface molecules which incorporate immunoglobulin domains:

They comprise cell adhesion molecules such as NCam, Axonin and NrCam, ligand binding domains of tyrosine kinase receptors such as the FGF-receptor ot the growth hormone receptor, a wide variety of phosphotyrosine phosphatases, membrane bound and secreted signalling molecules such as the semaphorins to name just a few.

Amongst the intracellular representatives of the immunoglobulin superfamily whose structures have been determined are the telokin domain of myosin light chain kinase in muscle cells and the PapD chaperone of E.coli.