The etiology of Crohn’s disease is unknown, although two major hypotheses have evolved: an infectious and an immunologic theory. The following statement(s) is/are true concerning the possible etiology of Crohn’s disease.
A.	The leading infectious agent thus far suggested is infection with a Mycobacterium species
B.	Strong evidence linking viral pathogens to Crohn’s disease has been developed
C.	Although many alterations in cellular and immune functions in patients with Crohn’s disease have been observed, no primary defect in the immune system has yet been identified
D.	The identification of antibodies to enterocytes provides strong support for the theory that Crohn’s disease is an autoimmune process
Answer:A
The etiology of Crohn’s disease is unknown, although two major hypotheses have evolved: an infectious and an immunologic theory. The following statement(s) is/are true concerning the possible etiology of Crohn’s disease.
A.	The leading infectious agent thus far suggested is infection with a Mycobacterium species B.	Strong evidence linking viral pathogens to Crohn’s disease has been developed C.	Although many alterations in cellular and immune functions in patients with Crohn’s disease have been observed, no primary defect in the immune system has yet been identified D.	The identification of antibodies to enterocytes provides strong support for the theory that Crohn’s disease is an autoimmune process