Pan B - Cell Marker : CD 22

CD22 (Siglec‑2) is a B‑cell–restricted transmembrane glycoprotein that helps regulate B‑cell receptor signaling and is used as a marker of the B‑cell lineage. It’s expressed on mature and late‑stage developing B cells (late pre‑B through memory B cells) but is typically absent on plasma cells. CD22 is used in immunophenotyping and as a diagnostic/therapeutic target in B‑cell leukemias and lymphomas.

Pan-B cell markers include CD19, CD20, CD22, CD79a and CD79b, and the B-lineage transcription factor PAX5. Surface immunoglobulins (sIgM/sIgD) and light chains (kappa/lambda) indicate B-cell receptor expression and clonality. CD45 is commonly used in flow panels to gate leukocytes. These markers identify B-lineage cells across maturation stages in both flow cytometry and immunohistochemistry.

CD20 is expressed on most B‑cell stages—from late pre‑B cells through mature and memory B cells—but it is not a true pan‑B‑cell marker. It is absent on early pro‑B cells, hematopoietic stem cells and terminally differentiated plasma cells (and many plasmablasts). Because CD20 is lacking on plasma cells, therapies targeting CD20 do not directly deplete antibody‑secreting plasma cells.

Common B‑cell CD markers include CD19 and CD20 (pan‑B markers), CD21 (CR2) and CD23 (follicular/maturation), CD22 and CD24, CD27 (memory), CD10 (immature/germinal‑center), CD38 and CD138 (activation/plasma cells), and CD79a/CD79b (B‑cell receptor components). Marker expression varies by developmental stage and activation state. These markers guide flow cytometry and immunophenotyping for B‑cell disorders.

CD22 (Siglec‑2) is a B‑cell–restricted surface protein expressed broadly on mature B‑lineage cells, including transitional, naïve, memory and germinal‑center B cells in peripheral blood and lymphoid tissues. Expression is low or absent on very early B‑cell precursors (pro‑B stage) and is downregulated or lost when B cells terminally differentiate into antibody‑secreting plasma cells.

CD22 stands for Cluster of Differentiation 22. It is a cell-surface molecule expressed primarily on mature B cells, functioning as an inhibitory co-receptor that regulates B-cell receptor signaling, limits activation, and helps maintain immune tolerance. CD22 is used as a diagnostic marker in immunophenotyping and a therapeutic target in certain B-cell malignancies and autoimmune conditions.