10-25-2010, 07:36 PM
MRL-lpr/lpr mutant mice are useful biomedical research models because of their increased susceptibility to autoimmune disease. These mice are characterized by a defect in the fas gene and a marked increase in T-lymphocyte accumulation as compared with wild-type animals. Based on these characteristics, which of the following is the most likely cause of the increased susceptibility of these mutants to autoimmune disease?
A. Decreased cell-cycle transit time for activated T lymphocytes
B. Decreased dependence on antigen-presenting cells for T-lymphocyte activation
C. Decreased responsiveness to clonal deletion signals in the thymic cortex
D. Increased responsiveness of mature T lymphocytes to antigenic stimulation
E. Increased thymocyte precursor proliferation in the bone marrow
F. Increased thymocyte proliferation rate in the thymic cortex
A. Decreased cell-cycle transit time for activated T lymphocytes
B. Decreased dependence on antigen-presenting cells for T-lymphocyte activation
C. Decreased responsiveness to clonal deletion signals in the thymic cortex
D. Increased responsiveness of mature T lymphocytes to antigenic stimulation
E. Increased thymocyte precursor proliferation in the bone marrow
F. Increased thymocyte proliferation rate in the thymic cortex