CD22 (Pan B Cell Marker)

CD22 is a B‑cell–specific surface glycoprotein (Siglec‑2) used as a marker of mature B lymphocytes in immunophenotyping. It regulates B‑cell receptor signaling and is present on most mature B cells but usually absent on pro‑B cells and plasma cells. Clinically, CD22 expression helps identify and target B‑cell leukemias and lymphomas.

Pan-B cell markers include surface and intracellular proteins consistently expressed across B-cell stages: CD19, CD20, CD22, CD79a/CD79b, and PAX5, often with surface immunoglobulin (IgM/IgD) positivity. Additional supportive markers used in diagnostics include CD45 and CD21, while markers like CD10 or CD23 help subtype B-cell populations rather than define the pan‑B lineage.

CD22 (Siglec‑2) is a B‑cell–restricted surface lectin expressed mainly on mature B cells — including naïve, memory, follicular and marginal‑zone subsets — from late pre‑B/immature stages onward. Expression is reduced on activated B cells and largely lost on plasmablasts and terminally differentiated plasma cells. It functions in B‑cell signaling and regulation of B‑cell receptor responses.

No — CD20 is a widely expressed B‑cell antigen present on most mature and many late precursor B cells, making it a common B‑cell marker and therapeutic target. However, it is not truly pan‑B: very early B‑lineage cells (some pro‑B) and terminally differentiated plasmablasts/plasma cells lack CD20, affecting diagnostic staining and response to anti‑CD20 therapies.

No — CD22 is a B‑cell–restricted surface lectin (SIGLEC‑2) found on mature B lymphocytes and typically lost during plasma cell differentiation. Normal T cells do not express CD22, so it is not used as a T‑cell marker. Rare aberrant or experimental contexts can show atypical CD22 detection, but physiologically CD22 is absent from conventional T‑cell populations.

CD22 stands for Cluster of Differentiation 22. It is a B‑cell–restricted transmembrane sialoglycoprotein (also called Siglec‑2) that acts as an inhibitory coreceptor, modulating B‑cell receptor signaling to help maintain tolerance and regulate activation. CD22 is also exploited as a diagnostic marker and therapeutic target in certain B‑cell malignancies and autoimmune disorders.