CD22expressing

CD22expressing refers to cells that display the B-cell surface protein CD22, also known as Siglec-2. CD22 is a transmembrane glycoprotein primarily expressed on mature B cells in peripheral blood, bone marrow, and lymphoid tissues, and is generally not found on T cells, NK cells, or most myeloid cells. It functions as an inhibitory co-receptor for B cell receptor signaling, containing ITIM motifs that recruit phosphatases such as SHP-1 to dampen activation after BCR engagement. CD22 also binds sialic acid–containing ligands, contributing to B cell homeostasis, antigen presentation, and trafficking within lymphoid organs.

Expression patterns can vary with B cell development, activation, and transformation. Malignant B cells in various B-lineage cancers often retain CD22 expression, which makes CD22 a useful diagnostic marker for identifying B-cell lineage and a potential therapeutic target. However, some subsets may downregulate CD22, and normal B cells are also CD22-positive, so therapies targeting CD22 can cause broad B-cell depletion.

Clinically, CD22 has become a target for several therapies in B-cell malignancies. Anti-CD22 monoclonal antibodies, antibody-drug conjugates such as inotuzumab ozogamicin, and recombinant immunotoxins like moxetumomab pasudotox have been developed or approved for relapsed or refractory disease. CD22-targeted approaches are also explored for autoimmune diseases and in the development of CD22-directed CAR T cells. The effectiveness of such therapies can be limited by antigen loss or downregulation and related toxicity risks.