A 34-year-old woman on infliximab for Crohn disease develops pulmonary tuberculosis. This therapy mainly inhibited which immunologic function?

• A. Activation of nuclear factor KB
• B. Direct toxicity to the causal organism
• C. Maintenance of granulomas
• D. Recruitment of segmented neutrophils

Answer: (C)

In the context of this question, the woman is receiving infliximab, an anti-TNF-alpha (tumor necrosis factor-alpha) monoclonal antibody used primarily for the treatment of autoimmune conditions like Crohn disease. TNF-alpha plays a crucial role in the immune response, particularly in maintaining granuloma formation in infections such as tuberculosis.

Granulomas are specialized structures that form in response to persistent antigens, including certain pathogens like Mycobacterium tuberculosis. They serve to wall off the infection and contain its spread. Infliximab's inhibition of TNF-alpha disrupts this process, leading to impaired granuloma formation and maintenance. This impairment can significantly reduce the body's ability to control infections like tuberculosis, making individuals more susceptible to reactivation of latent infections when they are on therapies that suppress TNF-alpha.

Therefore, by inhibiting TNF-alpha, infliximab primarily affects the maintenance of granulomas, which is critical for the body’s defense against certain intracellular pathogens, including tuberculosis. This highlights the important relationship between TNF-alpha and the immune system's ability to form and sustain these protective structures.