Disease Associated with Immune System
X-linked hyper IgM syndrome, resulting in high levels of serum IgM and low levels of serum IgG, is caused by a defect in CD40L expression. The specific immune event that would be prevented by a defective CD40L would be

failure of B cells to provide co-stimulation for Th2 activation
failure of Th2 cells to provide co-stimulation for B cell proliferation
activation of B cells by T-independent antigens
failure of Th2 cells to provide co-stimulation for B cell isotype switching

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Disease Associated with Immune System
Difficulties with somatic gene therapy arise from all of the following except

limited life span of more mature hematopoietic cells
GVHD caused by mature T cells in the transplanted cells
inserting a gene so that it will function properly
transducing genetic material into stem cells

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Disease Associated with Immune System
Chronic granulomatous disease results from a failure to perform oxidative burst. This deficiency would be most likely to interfere with

CTL killing of viruses
macrophage intracellular killing of bacteria
infected cell processing of virus peptides
dendritic cell activation to become a mature APC

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