Case study: Chronic granulomatous disease

In CGD, neutrophils and macrophages cannot destroy pathogens.

They are able to extravasate, respond to chemoattractant and can still phagocytose.

Diagnosis
Negative NBT.

Cause
Defect in NADPH oxidase.

Formation of granuloma
Due to the defect in NADPH oxidase, neutrophils are unable to kill bacteria and die shortly after a round of phagocytosis. These apoptotic neutrophils are engulfed by macrophages.

However, these bacteria are still alive and macrophages cannot kill them either. These macrophages become infected and accumulate. Some bacteria may be killed in the absence of functional NADH oxidase. It would be necessary for macrophages to present MHC II-peptide to be activated by Th.

A granuloma eventually forms with a central core of infected macrophages, surrounded by large macrophages that are interacting with T cells (mainly CD4). This mediates a chronic inflammatory response.