Page 38 - Headlines Histology2024_Neat

stained for lysosomal enzymes such as acid phosphatase.
3. They can be stains vitally with vital dyes such as trypan blue.
b. Stimulated or active macrophages

• They are large ovoid or spherical cells with eccentric kidney-shaped
nuclei and foamy cytoplasm. At the EM level, the macrophage nucleus
is indented with heterochromatin typically clumped around the nuclear
envelope.

• Actively phagocytic cells exhibit irregular cytoplasmic projections or
pseudopodia.

• The cytoplasm shows well-developed Golgi apparatus, abundant
lysosomes, many phagosomes and residual bodies, a few mitochondria
and variable amount of free ribosomes and rER.

Functions

• Phagocytosis.
• Antigen processing and antigen presentation thus participating in both

humoral and cell mediated immunity.
• Synthesis and secret many substances such as lysozyme (antibacterial

agent), interferon (antiviral), interleukin that are essential for the
proliferation of T and B-lymphocytes.
• Many macrophages can fuse with each other forming large
multinucleated cells called foreign body giant cells that can engulf large
foreign bodies.
• The macrophage and blood monocytes are considered identical.
Monocytes circulate in the blood then they migrate to the connective
tissue where they are called macrophages.
• The macrophages are present practically in all organs, constituting a
diffuse system called mononuclear phagocyte system. They may have
other names such as: osteoclasts in bone; monocytes in blood; dust cells

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