Macrophage

Steps of a macrophage ingesting a pathogen:
a. Ingestion through phagocytosis, a phagosome is formed
b. The fusion of lysosomes with the phagosome; the pathogen is broken down by enzymes
c. Waste material is expelled or assimilated (the latter not pictured)
Parts:
1. Pathogens
2. Phagosome
3. Lysosomes
4. Waste material
5. Cytoplasm
6. Cell membrane

Macrophages are white blood cells within tissues, produced by the differentiation of monocytes.

Monocytes and macrophages are phagocytes, acting in general immunity. They also trigger specific defense mechanisms (adaptive immunity) of vertebrates.

Their role is to phagocytose (engulf and then digest) cellular debris and pathogens either as stationary or as mobile cells. They also stimulate lymphocytes and other immune cells to respond to the pathogen,

Life cycle

When a monocyte enters damaged tissue through the wall of a blood vessel it changes to become a macrophage. Monocytes are attracted to a damaged site by chemical substances, triggered by a range of stimuli. At some sites such as the testis, macrophages have been shown to populate the organ through proliferation.

Unlike short-lived neutrophils, macrophages survive longer in the body, up to several months.

Macrophage Media

• 

  Drawing of a macrophage when fixed and stained by giemsa dye

• 

  A macrophage stretching its "arms" (filopodia) to engulf two particles, possibly pathogens, in a mouse (trypan blue exclusion staining).

• 

  Micrograph of a melanophage, which is a macrophage containing melanin pigment. It is surrounded by red blood cells. H&E stain.

• An active J774 macrophage is seen taking up four conidia in a co-operative manner. The J774 cells were treated with 5 ng/ml interferon-γ one night before filming with conidia. Observations were made every 30s over a 2.5hr period.

• Two highly active alveolar macrophages can be seen ingesting conidia. Time lapse is 30s per frame over 2.5hr.