Which of the following type of cells give rise to macrophages?: (A) Neutrophils, (B) Monocytes, (C) Lymphocytes, (D) Reticulo endothelial cells.
Answer is B. Monocytes formed in the bone marrow are precursors of tissue macrophages. After an intravascular stay of 3 days, monocytes migrate from the blood into tissues. In the tissues, monocytes undergo differentiation into macrophages.