HPS patients with active colitis will be enrolled into this prospective treatment study. Endpoints for the immunopathogenesis studies will include baseline measurements of and changes in immune cell populations, cytokine, and chemokine expression. In the blood and gut mucosa. Endpoints for the study of response to treatment will include changes in clinical, endoscopic, and histologic scores as well as the rate and severity of adverse events. Descriptive summary statistical analysis (n, mean, median, standard deviation, minimum and maximum range) and simple correlations of clinical response variables with immune parameters will be done.