The correct option is Neutrophils.
Explanation
Leukocytes, or White Blood Cells (WBCs), are classified into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes). The differential leukocyte count measures the percentage of each type present in the total WBC count.
Detailed Analysis of Abundance:
- Neutrophils: These are the most abundant leukocytes, constituting approximately 60-65% of the total WBC count. They act as the primary defense against bacterial and fungal infections through phagocytosis.
- Lymphocytes: Although not listed in the options, these are the second most abundant, making up about 20-25%. They are crucial for specific immune responses (B and T cells).
- Monocytes: These constitute approximately 6-8% of the total count. They are the largest leukocytes and differentiate into macrophages in tissues.
- Eosinophils: These make up about 2-3%. Their numbers typically increase during allergic reactions and parasitic infections.
- Basophils: These are the least abundant leukocytes, constituting only 0.5-1%. They are involved in inflammatory reactions by secreting histamine, serotonin, and heparin.
Key Takeaway:
The decreasing order of leukocyte abundance in human blood is: Neutrophils > Lymphocytes > Monocytes > Eosinophils > Basophils.