What effect does the absence of NADPH in immune cells primarily have?

The absence of NADPH in immune cells primarily prevents oxidative burst and killing activity. NADPH plays a crucial role in the metabolic pathway that generates reactive oxygen species (ROS) during the oxidative burst, which is an essential mechanism used by phagocytes such as neutrophils and macrophages to destroy ingested pathogens.

During an immune response, NADPH is generated through the pentose phosphate pathway and is used by the enzyme NADPH oxidase to convert oxygen into superoxide radicals, which are then further transformed into other reactive species. These reactive oxygen species are vital for effectively killing pathogens and facilitating microbial destruction. Without sufficient NADPH, the oxidative burst cannot occur, leading to impaired microbicidal activity and potential susceptibility to infections.

The other options do not directly relate to the primary function of NADPH in the context of immune response. While DNA replication, protein synthesis, and inflammatory responses are important aspects of cellular function and immune activity, they are not the direct effects associated with the loss of NADPH in immune cells.