After circulating in peripheral blood, which cell becomes a tissue macrophage whose main function is phagocytosis?

The correct choice is based on the development and function of monocytes in the immune system. Monocytes circulate in the bloodstream and, upon migrating into tissues, differentiate into macrophages. These macrophages play a critical role in the immune response, primarily through their function of phagocytosis, where they ingest and destroy pathogens, dead cells, and debris.

This transformation from monocyte to macrophage is crucial because it allows the immune system to effectively respond to infections at the site of injury or inflammation. The phagocytic activity of macrophages is essential for maintaining homeostasis and initiating tissue repair, as well as orchestrating the overall immune response.

Other cell types listed have different primary roles. Neutrophils are also phagocytic but are primarily involved in acute inflammation and respond rapidly to sites of infection. Basophils are mainly involved in allergic reactions and releasing histamine, while eosinophils play a crucial role in combating parasitic infections and are also involved in allergic reactions. Therefore, the specific development and function of monocytes leading to macrophages underscore why this choice is the correct answer.