MLAB 1415: H EMATOLOGY Chapter 7: Leukocytes Part Two

MONOCYTES Monopoiesis - the production and development of monocytes, macrophages and their precursors. Monocytes are produced in the bone marrow.

MONOCYTES Differentiation & maturation Produced from CFU-GM Can further differentiate into macrophages in the tissues Lifespan P.B ~ 8 hours Tissue Regulation Production primarily regulated by cytokines GM-CSF IL-3 M-CSF

M ONOCYTES /M ACROPHAGES Function Protect the host from infectious agents or pathogens via innate and adaptive immune response Phagocytosis Scavengers

M ATURATION OF THE MONOCYTIC SERIES Monoblast Size: 12-20µm Cytoplasm Blue, moderate amount No granules Nucleus Round, oval or slightly folded Eccentric Reddish-purple Chromatin fine and lacy Vacuoles may be present 1-2 nucleoli N:C ratio = 4:1

M ATURATION OF THE MONOCYTIC SERIES Promonocyte (difficult to discern) Size: 12-20µm Cytoplasm Paler gray-blue and abundant “Bleb-like” pseudopods at periphery May contain fine red “dust-like” particles, azurophilic granules Vacuoles may be present Nucleus Round with chromatin creases or brain-like folding Central Reddish-purple with light clumping of chromatin 0-2 nucleoli N:C ratio = 3:1 or 2:1

P ROMONOCYTE

M ATURATION OF THE MONOCYTIC SERIES Mature monocyte Normal in circulation: 2-9% Size: 12-20µm Cytoplasm Pale gray-blue and abundant Bleb-like pseudopods at periphery, variable shape Numerous fine pale red dustlike granule scattered throughout Vacuoles common Nucleus Increased folding or elongated Central Purplish with finer clumped chromatin No nucleoli N:C ratio = Variable

M ONOCYTE

M ONOCYTES …THINK…. Fine, Lacy ChromatinGround Glass Cytoplasm

M ACROPHAGES Once the monocyte enters the tissues, it becomes a macrophage Size:15-80µm Cytoplasm Gray-blue and abundant Ragged edges Vacuoles common Nucleus Round with netlike appearance Purplish with finer clumped chromatin Nucleoli appear

M ACROPHAGES IN V ARIOUS T ISSUES Macrophage alias’ Histiocytes in the loose connective tissue Kupffer cells in the liver Osteoclasts in the bone Microglial cells in the nervous system Also scattered throughout the body in all organ tissues (spleen, lung, abdomen, etc)

M ACROPHAGE

R EFERENCES MacKenzie, S., & Lynne, W. J. (2010). Clinical Laboratory Hematology. Upper Saddle River: Pearson Education, Inc.