CD81

By Jamshed Arslan, Pharm. D., PhD.

Exosomes are spherical to cup-shaped bilayered membrane enclosed nanosize vesicles (30-100 nm) which have the ability to shuttle active cargoes between cells. Johnstone et al. 1987 pioneered in documenting the generation of exosomes in differentiating reticulocytes as a result of the fusion of multi-vesicular endosomes/MVBs with the plasma membrane.

CD19 is a cell surface protein member of the large immunoglobulin superfamily that complexes with CD21, CD81, and CD225 in the membrane of mature B-cells. A major function of CD19 is to assemble with the antigen receptor of B-lymphocytes to decrease the threshold for receptor-dependent stimulation, thus enhancing the specificity and sensitivity of B-cells towards antigens. CD19 plays a large role in regulating B-cell growth.

Target of the antiproliferative 1 (TAPA1), also known as CD81, is found in the plasma membrane in lymphocytes and plays an important role in the regulation of lymphoma cell growth. This transmembrane 4 superfamily (TM4SF) protein is primarily found on CD4⁺CD8⁺ thymocytes as well as broadly in the periphery, with high-level expressed in cell cohorts such as B-cells, NK cells, macrophages, and dendritic cells.