CD78 is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 expressed on the surface of some immature and all mature B-cells. It is considered a pan-B cell antigen

Antigen

An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...

. Other names include Cdw78, Ba antigen, Leu21 and LO-panB-a.

Expression

CD78 is expressed on all stages of B cell development from pre-B cell through plasma cells. Its expression is strongest on activated B cells.

It is also present on tissue macrophage

Macrophage

Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

s and on epithelial cells.

Clinical significance

With flow cytometry

Flow cytometry

Flow cytometry is a technique for counting and examining microscopic particles, such as cells and chromosomes, by suspending them in a stream of fluid and passing them by an electronic detection apparatus. It allows simultaneous multiparametric analysis of the physical and/or chemical...

, it can be used to detect B cells during many stages of their development. It is one of relatively few markers usefully expressed on plasma cells, and when combined with detection of markers such as CD22, can be used to determine the relative proportion of plasma cells.