Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to X-linked hyper IgM syndrome ?
    ### Response:
    Mutations in the CD40LG gene cause X-linked hyper IgM syndrome. This gene provides instructions for making a protein called CD40 ligand, which is found on the surface of immune system cells known as T cells. CD40 ligand attaches like a key in a lock to its receptor protein, which is located on the surface of immune system cells called B cells.
    