[3] Plasma cells are large lymphocytes with abundant cytoplasm and a characteristic appearance on light microscopy.

They have basophilic cytoplasm and an eccentric nucleus with heterochromatin in a characteristic cartwheel or clock face arrangement.

Their cytoplasm also contains a pale zone that on electron microscopy contains an extensive Golgi apparatus and centrioles.

Abundant rough endoplasmic reticulum combined with a well-developed Golgi apparatus makes plasma cells well-suited for secreting immunoglobulins.

[12] However, continued exposure to antigen through those low levels of immunoglobulin is important, as it partly determines the cell's lifespan.

LLPC mainly reside in the bone marrow for a long period of time and secrete antibodies, thus providing long-term protection.

[19][20] The plasma cell survival niche is defined by a combination of cellular and molecular factors and though it has yet to be properly defined, molecules such as IL-5, IL-6, TNF-α, stromal cell-derived factor-1α and signalling via CD44 have been shown to play a role in the survival of LLPC.

[21] LLPC can also be found, to a lesser degree, in gut-associated lymphoid tissue (GALT), where they produce IgA antibodies and contribute to mucosal immunity.

Recent findings suggest that plasma cells in the gut do not necessarily need to be generated de novo from active B cells but there are also long-lived PC, suggesting the existence of a similar survival niche.

The absence of antigens and the depletion of B cells does not appear to have an effect on the production of high-affinity antibodies by the LLPC.

[33] Multiple myeloma is frequently identified because malignant plasma cells continue producing an antibody, which can be detected as a paraprotein.

[34] Common variable immunodeficiency is thought to be due to a problem in the differentiation from lymphocytes to plasma cells.

[citation needed] Primary amyloidosis (AL) is caused by the deposition of excess immunoglobulin light chains which are secreted from plasma cells.