A. Whole blood from the index case and a healthy control were stained for intracellular XIAP protein and gated for monocytes, lymphocytes, and granulocytes. Histograms show the lack of XIAP protein staining in all leukocyte subsets. B. Isolated peripheral blood mononuclear cells were stimulated with either LPS as a positive control, L18-MDP as the experimental condition, or PBS as an unstimulated control. Gated monocytes from the control show upregulation of both TNF-a or IL-8 expression when stimulated with either LPS or muramyl dipeptide (MDP), but the patient did not show any upregulation with MDP stimulation. Normal responses noted with LPS indicating the patient’s monocytes are viable and responsive.