Which leukocyte leaves the circulation to become a macrophage in tissues?

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Multiple Choice

Which leukocyte leaves the circulation to become a macrophage in tissues?

The main idea is that macrophages in tissues come from circulating monocytes that exit the bloodstream and differentiate once they enter tissues. Monocytes patrol the blood, and when they migrate into tissues during inflammation or routine turnover, they become macrophages. These macrophages are long-lived, specialized for phagocytosis, and also act as antigen-presenting cells helping to activate the adaptive immune response. Lymphocytes are the cells of the adaptive immune system and don’t morph into macrophages. Basophils release inflammatory mediators like histamine rather than becoming macrophages. Neutrophils are quick responders to infection and, after phagocytosis, typically die off rather than transforming into macrophages. So, the leukocyte that leaves circulation to become a macrophage in tissues is the monocyte.

The main idea is that macrophages in tissues come from circulating monocytes that exit the bloodstream and differentiate once they enter tissues. Monocytes patrol the blood, and when they migrate into tissues during inflammation or routine turnover, they become macrophages. These macrophages are long-lived, specialized for phagocytosis, and also act as antigen-presenting cells helping to activate the adaptive immune response.

Lymphocytes are the cells of the adaptive immune system and don’t morph into macrophages. Basophils release inflammatory mediators like histamine rather than becoming macrophages. Neutrophils are quick responders to infection and, after phagocytosis, typically die off rather than transforming into macrophages.

So, the leukocyte that leaves circulation to become a macrophage in tissues is the monocyte.

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