A 5-year-old male becomes ill with a severe cough. Histologic examination reveals a bacterial infection, and further laboratory testing reveals cell membrane damage and decreased protein synthesis. Which of the following is the most likely cause of this illness?

The normal host defense mechanisms against infection include (1) normal skin and mucous membranes, (2) phagocytic system, (3) humoral immunity, and (4) cellular immunity. The compromised host is an individual who has one or more defects in these defense mechanisms. (Source: NIH.gov)