Question

Match each description with a white blood cell in the key. a. lymphocytes d. monocytes b. neutrophils e. eosinophils c. basophils Largest, no granules, become macrophages.

Short answer

The white blood cell that matches the description "Largest, no granules, become macrophages" is \(d.\) Monocytes.

Step-by-step solution

Understanding the Description

The description is about a type of white blood cell that is the largest in size, does not have granules in its cytoplasm, and can transform into macrophages (a type of immune cell that engulfs and destroys foreign substances, dead cells, and cellular debris).

Lymphocytes

\(a.\) Lymphocytes are white blood cells responsible for adaptive immune responses. They are divided into B cells and T cells. They do not fit the description because they are not the largest and don't become macrophages.

Neutrophils

\(b.\) Neutrophils are granulocytes, meaning they contain granules in their cytoplasm. They are the most abundant type of white blood cells and are essential in fighting bacterial infections. However, they don't fit the description because they have granules.

Basophils

\(c.\) Basophils are also granulocytes that play a role in allergic reactions and inflammation. Similarly, they do not fit the description because they also contain granules in their cytoplasm.

Monocytes

\(d.\) Monocytes are large white blood cells that do not have granules. They can differentiate into macrophages and play a significant role in phagocytosis (engulfing and digesting foreign substances and cellular debris). This white blood cell fits the provided description.

Eosinophils

\(e.\) Eosinophils are granulocytes involved in combating parasitic infections and participating in allergic reactions. They do not fit the description because they contain granules in their cytoplasm.

Conclusion

The white blood cell that matches the description "Largest, no granules, become macrophages" is \(d.\) Monocytes.

Key concepts

Lymphocytes

Lymphocytes are a crucial component of the immune system, tasked with protecting the body against various pathogens. They are a subset of white blood cells and primarily participate in the adaptive immune response. This means they are responsible for detecting and remembering specific pathogens to mount stronger defenses in future infections.

There are two main types of lymphocytes:

• B cells: Responsible for producing antibodies which target and neutralize pathogens.
• T cells: Play a role in directly attacking infected cells, coordinating the immune response, and regulating other immune cells.

It's important to note that lymphocytes are not the largest of the white blood cells and they do not transform into macrophages. Instead, they focus on disabling pathogens with targeted strategies, unlike some other white blood cell types that engulf and digest invaders.

Neutrophils

Neutrophils are the most abundant type of white blood cells, accounting for about 50-70% of all white blood cells in our body. They are a first line of defense in the immune system and are especially efficient in fighting off bacterial infections.

As granulocytes, neutrophils contain granules in their cytoplasm that are packed with enzymes and antimicrobial substances. These granules release their contents to destroy pathogens once engulfed. Despite their effectiveness, neutrophils are not the correct fit for every problem due to their specific characteristics:

• They contain granules, which categorize them differently in exercises about "no granules" cells.
• They do not transform into macrophages, but they engage pathogens directly to eliminate them.

Neutrophils act quickly but have a short life span, emphasizing the body's reliance on other cells for prolonged immune responses.

Monocytes

Monocytes stand out because of their size — they are the largest type of white blood cell and have no granules in their cytoplasm. Their primary role includes differentiating into macrophages or dendritic cells upon migrating to tissues.

Here are some key functions of monocytes:

• They transform into macrophages, which are crucial for engulfing and digesting foreign substances, including bacteria and dead cells.
• As macrophages, they play a significant role in both initiating and resolving inflammation.
• Monocytes also participate in antigen presentation, helping to activate T cells and thus bridging the gap between innate and adaptive immunity.

Given their ability to differentiate into macrophages without having cytoplasmic granules, monocytes are the correct answer for identifying the cell type from the "largest, no granules, become macrophages" description.

Basophils

Basophils are another type of white blood cell under the category of granulocytes, and they are an essential player in the body's response to allergens and during inflammatory reactions. Despite their presence in smaller numbers compared to other white blood cells, they perform vital functions:

• Basophils release histamine during allergic reactions, which helps mediate inflammation and increase blood flow.
• They contain granules filled with histamine and other mediators essential for the body's response to external allergens.
• These cells play a supportive role by assisting other white blood cells in reacting to pathogens.

However, because they contain granules and do not become macrophages, basophils are not a match for the "no granules" description in the exercise.

Eosinophils

Eosinophils, like basophils and neutrophils, are categorized as granulocytes due to the granules found within their cytoplasm. These granules are crucial in responding to parasitic infections and in modulating allergic reactions.

The primary roles of eosinophils include:

• Combating parasitic invasions, particularly those caused by parasitic worms, which they neutralize using the enzymes in their granules.
• Participating in the allergic inflammation process, often being one of the culprits behind tissue damage due to allergies.
• Eosinophils also help modulate the intensity and duration of immune responses.

As with other granulocytes, eosinophils contain granules, which make them unsuitable for the "largest, no granules, become macrophages" categorization in exercises like this.