Macrophages are leukocytes (white blood cells) which are present in all tissues of the body. Macrophages develop from bone marrow precursors which mature and enter the bloodstream as monocytes.
| This
stained blood smear shows a blood monocyte staining purple and
red blood cells staining pink. Note the large bi-lobed nucleus of the monocyte. The smaller purple cell fragments are platelets. |
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Monocytes are recruited into different tissues
where they differentiate into tissue resident
macrophages which perform important functions in tissue homeostasis
and the immune response.