Question

Macrophages are derived from
a. Neutrophils
b. Lymphocytes
c. Monocytes
d. Basophils

Answer 1

Hint: Macrophages are the large and mononuclear cells that function as phagocytic cells. Macrophages originate in the bone marrow and move to the blood as precursor cells that become macrophages specific to the tissues where they are derived from their precursor cells. These precursor cells are also large and mononuclear leukocyte cells.

Complete step-by-step solution:
1. Monocytes are the largest leukocytes (white blood cells), having a single large nucleus. They are formed in the bone marrow and released into the bloodstream. These monocytes stay in the bloodstream until they receive signals from a particular tissue. Once inside the tissue, they differentiate into macrophages specific for that particular tissue.
2. Macrophages have different names depending upon the tissues where they are derived from their precursors (monocytes). For example mesangial cells for macrophages of the kidney, alveolar macrophage in lungs, kupffer cells in the liver, microglia in the brain, etc.

Additional Information:
1. Macrophages play an important role in the immune system, where they are formed in response to an infection or presence of dead and damaged cells. Once formed from monocytes these large mononuclear cells recognize the target cell and engulf it through phagocytosis and destroy the target cell.
2. Macrophages once formed can survive for a few months and are also involved not just as the first line of defense during infection but are also involved in the development of non-specific innate immunity.

Note: Leukocytes form the major part of the immune system. Hematopoiesis is a process of formation of blood cells and thus leukocytes are formed from hematopoietic stem cells in the bone marrow. Leukocytes are of two types: granulocytes (like neutrophils, basophils, mast cells and eosinophils) and mononuclear leukocytes (like lymphocytes, monocytes, macrophages, and dendritic cells).