During infection, the count increases.

Question

Accepted Answer

The correct option is 2:

Leucocytes, commonly known as White Blood Cells (WBCs), are the fundamental component of the body's immune system, serving as the main defense mechanism against foreign invaders such as bacteria, viruses, and parasites. When an infection occurs, the body initiates an immune response. This process, known as leukocytosis, involves the rapid proliferation and mobilization of WBCs from the bone marrow and lymphoid tissues to the site of infection. These cells recognize and destroy the pathogens through processes like phagocytosis (engulfing the pathogen) or by producing antibodies. Therefore, a high leucocyte count is a clinical indicator of an active infection or inflammation in the body.

The incorrect option is 1:
Erythrocytes (Red Blood Cells or RBCs) are primarily responsible for transporting oxygen throughout the body. Their count does not typically increase during an acute infection; in fact, prolonged infection or inflammation can sometimes lead to a mild decrease in RBC count, a condition known as anemia of chronic disease.

The incorrect option is 3:
Platelets are small blood components primarily involved in blood clotting (hemostasis). While their count can sometimes be affected by severe inflammation or certain chronic infections, their primary function is not fighting pathogens, and their increase is not the defining response to a general infection.

The incorrect option is 4:
Haemoglobin is a protein found inside erythrocytes that binds to oxygen. Its concentration is related to the oxygen-carrying capacity of the blood, not the immune response. Similar to the erythrocyte count, haemoglobin levels do not characteristically increase during an infectious episode.