Tspan33, a member of the tetraspanin family, is a transmembrane protein. Tetraspanins form membrane microdomains and play roles in cellular processes like migration and adhesion. Tspan33 is involved in regulating ADAM10, a "molecular scissor" that cleaves extracellular regions of membrane proteins. It also participates in pathways such as NOTCH signaling, which is important in cell fate decisions [2,3,6,7,8].

Tspan33 is not expressed in resting B cells but is strongly induced in primary human B cells following activation. It is expressed in several lymphomas, including Hodgkin's and Diffuse large B cell lymphoma, as well as in some autoimmune diseases where B cells are involved, like rheumatoid arthritis, systemic lupus erythematosus (SLE), and in spleen B cells from MRL/Fas(lpr/lpr) mice (a mouse model of SLE). In macrophages, its expression increases in response to TLR signaling and IFN-γ, and it modulates TLR-induced proinflammatory gene expression. In B-lymphocytes, it regulates endocytosis and migration by affecting plasma membrane tension. In platelets, Tspan33, along with Tspan15, plays a role in the cleavage of the platelet-activating collagen receptor GPVI by ADAM10 [1,2,3,4,5].

In conclusion, Tspan33 has diverse functions in different cell types. Its role in B-cell activation, lymphoma, autoimmune diseases, macrophage activation, B-lymphocyte migration, and platelet-related processes has been revealed through various studies. These findings suggest Tspan33 could be a potential diagnostic biomarker or therapeutic target for certain B-cell lymphomas and autoimmune diseases [1].