Final answer:
A white blood cell with a kidney-shaped nucleus, capable of phagocytosis, is likely a macrophage. Macrophages are large, highly efficient phagocytes and part of the immune system's frontline defense, ridding the body of pathogens and worn-out cells.
Step-by-step explanation:
White Blood Cell with Kidney-Shaped Nucleus
The white blood cell (WBC) showing a kidney-shaped nucleus and capable of phagocytosis is likely a macrophage. Macrophages develop from monocytes and are highly efficient phagocytes that engulf a substantial number of pathogens or other cells. These cells spend much of their time within the interstitial fluid in the tissues of the body, acting as scavengers to rid tissues of worn-out cells and pathogens and as antigen-presenting cells to activate the adaptive immune system.
On the contrary, lymphocytes such as NK cells have large nuclei but are not characterized by a kidney-shaped nucleus and are predominantly involved in destroying cancerous or virus-infected host cells. Neutrophils, which are also phagocytes and have multilobed nuclei, are the most numerous type and they arrive first at the site of infection. They are extremely important during acute inflammation, and they have a limited lifespan after phagocytizing just a few pathogens.
Phagocytosis in the Immune System
Phagocytosis is a crucial mechanism in the immune system where phagocytes engulf pathogens to form a phagosome, which then fuses with a lysosome containing digestive enzymes. This process effectively kills many pathogens, although certain bacteria such as Mycobacteria tuberculosis may be resistant to these enzymes. Major phagocytes of the immune system include macrophages, neutrophils, and dendritic cells.