Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) complement factor I deficiency ?
    ### Response:
    Complement factor I deficiency is a disorder that affects the immune system. People with this condition are prone to recurrent infections, including infections of the upper respiratory tract, ears, skin, and urinary tract. They may also contract more serious infections such as pneumonia, meningitis, and sepsis, which may be life-threatening.
    