Parents Who Were Distantly Related to Each Other Brought Their

Parents who were distantly related to each other brought their 11-week-old infant Kristen to the emergency room after she had a seizure accompanied by a persistently high fever and running nose.Her liver and spleen were palpable (hepatosplenomegaly) .Laboratory tests revealed abnormally high levels of lymphocytes,and of the cytokines IFNγ,TNF-α,and IL-6.Conversely,levels of hemoglobin and platelets were abnormally low.Bone marrow aspiration showed the presence of macrophages containing phagocytosed red blood cells and numerous large granular lymphocytes.Molecular analysis was carried out to confirm the physician's suspicion of a congenital immunodeficiency.A frameshift mutation in the perforin gene PRF1 was found on both chromosomes.Kristen was diagnosed with the rare,potentially life-threatening disease known as familial hemophagocytic lymphohistiocytosis (FHL) .Cytotoxic and aggressive immunosuppressive chemotherapy was administered followed by a matched unrelated hematopoietic stem cell transplant.Two years later Kristen is a healthy toddler.Which of the following would not be consistent with the etiology of FHL?

A) impaired cytotoxic activity of CD8 T cells
B) inhibition of transcriptional activators required for IL-2 synthesis
C) inability to kill virus-infected cells
D) persistent activation of CD8 T cells causing secretion of large amounts of IFN-γ
E) IFN-γ activation of macrophages which in turn drives the production of IL-6,TNF-α,and other pro-inflammatory molecules.