Crohn's and Rituxan (B Cell depletion)

Dear Doctor,
My 22 year old son just completed treatment for Burkitts Lymphoma. He has also had Crohn's since the age of 15. I have 2 questions to ask if I could. He had been on low dose 6-mp for his Crohn's. Could this have caused Burkitts? Do you know of any data in the Crohn's field of research where these two are connected? My second question is could the fact that my son's B cells have been depleted due to chemo and use of Rituxan, help his Crohn's stay in remission for awhile? Is there any research out there that you know of that supports Rituxan useage and depleting B cells in an effort to keep Crohn's in remission. Thank you so much for your help. My son's case is quite perplexing due to the fact that Burkitts and Crohn's are both involved. Please let me know of any research that you have come across. Thank you. Deanna Davis