Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Immunodeficiency with hyper IgM type 1 ?
    ### Response:
    What causes hyper IgM syndrome? A flawed gene (or genes) in T-cells (a type of white blood cell that is part of the immune system and helps the body fight diseases or harmful substances) is responsible for hyper IgM syndrome. The faulty T-cells do not give B-cells a signal they need to switch from making IgM to IgA and IgG.
    