Which of the following is the least and most abundant leucocytes in human blood, respectively ?

Options

A. Basophils , Neutrophils
B. Neutrophils , Basophils
C. Eosinophil's , Neutrophils
D. Basophils, Lymphocytes

Answer

To solve the question regarding the least and most abundant leukocytes in human blood, we can follow these steps:

### Step 1: Identify the types of leukocytes
Leukocytes, or white blood cells (WBCs), are crucial components of the immune system. There are five major types of leukocytes:
1. Neutrophils
2. Eosinophils
3. Basophils
4. Monocytes
5. Lymphocytes

### Step 2: Determine the abundance of each type
- **Neutrophils**: These are the most abundant leukocytes, making up about 60-70% of the total WBC count. They are primarily involved in phagocytosis, helping to fight infections.
- **Eosinophils**: These cells are involved in allergic reactions and parasitic infections, constituting about 1-4% of the WBC count.
- **Basophils**: These are the least abundant leukocytes, making up less than 1% of the total WBC count. They are involved in inflammatory responses and release histamine and heparin.
- **Monocytes**: These are larger WBCs that differentiate into macrophages and dendritic cells, making up about 2-8% of the WBC count.
- **Lymphocytes**: These cells are crucial for the adaptive immune response, accounting for about 20-40% of the WBC count.

### Step 3: Identify the least and most abundant leukocytes
From the information gathered:
- The **least abundant** leukocyte is **Basophils**.
- The **most abundant** leukocyte is **Neutrophils**.

### Step 4: Present the answer in the required format
The question asks for the least and most abundant leukocytes in human blood, respectively. Therefore, the answer is:
- **Least abundant**: Basophils
- **Most abundant**: Neutrophils

### Final Answer
The least and most abundant leukocytes in human blood, respectively, are Basophils and Neutrophils.

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