Plasma cells (or plasmocytes) are white blood cells produced from B-lymphocytes.
Plasma cells are a part of the immune system. Their function is the secretion of special immunoglobulins (antibodies). Upon stimulation by an antigen, B-lymphocytes are released into the lymph nodes where they begin to differentiate into plasmocytes and memory cells which are able respond to the presence of the antigen in months or even years after the first invasion.
The lifespan of a plasmocyte is just a few days, however memory cells can live for years and even for a lifetime. If exposure to the same antigen occurs again, memory cells start fighting it immediately by synthetizing large amounts of antibodies without having to spend their time identifying the antigen.
Normally, the lack of plasma cells is typical in healthy adults, while small amounts of plasmocytes are a common finding in children.
Plasma cells are in most cases associated with viral infections (measles, chicken pox, infectious mononucleosis, infectious hepatitis).