Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Microscopic Colitis: Collagenous Colitis and Lymphocytic Colitis ?
    ### Response:
    The exact cause of microscopic colitis is unknown. Several factors may play a role in causing microscopic colitis. However, most scientists believe that microscopic colitis results from an abnormal immune-system response to bacteria that normally live in the colon.
    