Phagocytic cells, particle accumulation

Cells of the immune system serve many different purposes, and they support each other to form complex loops. Phagocytes, or white blood cells, ingest bacteria, viruses, and foreign particles, and digest them when possible (figure). This often kills the phagocytes, which accumulate to form the pus at the site of an infection. Lymphocytes produce antibodies and kill target cells with lethal chemicals. There are several different types of each class of cells. 

Particle size. Particles greater than 7 pm are larger than blood capillaries ( 6 pm) and become entrapped in the capillary beds of the lungs (which may have fatal effects). The majority of particles that pass the lung capillary bed accumulate in the elements of the RES (spleen, liver and bone marrow). The degree of splenic uptake increases with particle size. Removal of particles > 200 nm is due to a non-phagocytic process (physical filtration) in the spleen and phagocytosis (by Kupffer cells) by the liver. Particles < 200 nm decreases splenic uptake and the particles are cleared by the liver and bone marrow. Colloidal particles not cleared by the RES can potentially exit the blood circulation via the sinusoidal fenestration of the liver and bone marrow. 

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