This cell is the largest white blood cell. It lacks cytoplasmic granules and has a kidney-shaped nucleus. A) neutrophil B) eosinophil C) basophil D) monocyte
The correct answer and explanation is:
The correct answer is D) monocyte.
Monocytes are the largest type of white blood cells and play an essential role in the immune system. They are characterized by their large, kidney-shaped or horseshoe-shaped nucleus, which distinguishes them from other types of white blood cells. Unlike granulocytes (such as neutrophils, eosinophils, and basophils), monocytes do not contain cytoplasmic granules, making them agranulocytes.
Monocytes circulate in the blood for about one to three days before migrating into tissues, where they differentiate into macrophages or dendritic cells. Macrophages are crucial for phagocytosis, a process where they engulf and digest foreign invaders like bacteria and viruses, as well as dead cells and debris. Dendritic cells, on the other hand, are involved in presenting antigens to T-cells, helping to initiate the adaptive immune response.
Neutrophils, eosinophils, and basophils, on the other hand, are granulocytes, meaning they have visible cytoplasmic granules that contain enzymes and other chemicals important for immune defense. Neutrophils are the most abundant type of white blood cell and are the first responders to infections, particularly bacterial ones. Eosinophils are involved in combating parasitic infections and allergic reactions, while basophils release histamine during inflammatory responses.
Monocytes’ primary role in immunity is to support long-term defense mechanisms by transforming into tissue-resident macrophages that can persist in the body for long periods. Their ability to differentiate into macrophages or dendritic cells makes them versatile players in both innate and adaptive immune responses.