Tspan33 is a gene encoding a transmembrane protein and a member of the tetraspanin family. It is involved in multiple cellular processes. Tspan33 is crucial in the context of B-cell activation, as it is not expressed in resting B cells but strongly induced upon activation. It also plays a role in the regulation of ADAM10-related functions and is associated with NOTCH signaling pathway, which is important in macrophage activation [1,3,6,7,8].

Tspan33 is expressed in activated B cells, transitional and memory B cells, and several lymphomas, such as Hodgkin's and Diffuse large B cell lymphoma. It is also expressed 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, Tspan33 expression increases in response to TLR signaling and IFN-γ, and its overexpression increases ADAM10 maturation. In B-lymphocytes, it regulates endocytosis, migration, and affects 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 is a key regulator in B-cell activation, macrophage activation, and lymphocyte migration. Its role in lymphomas and autoimmune diseases makes it a potential diagnostic biomarker and therapeutic target. The findings from various cell-based and in vivo-like mouse model-related studies (such as the SLE mouse model) have enhanced our understanding of Tspan33's functions in these biological processes and disease conditions [1,3,4].