CD45 / LCA (Leukocyte Common Antigen)

CD45 (leukocyte common antigen) is a transmembrane protein tyrosine phosphatase expressed on all nucleated hematopoietic cells. Encoded by PTPRC, it regulates antigen‑receptor signaling in T and B cells by modulating Src family kinases, influencing activation and development. Multiple isoforms (e.g., CD45RA, RO) arise from alternative splicing and serve as differentiation markers in flow cytometry and immunophenotyping.

Yes. LCA (leukocyte common antigen) is the same as CD45 — a family of transmembrane protein tyrosine phosphatase isoforms expressed on nearly all nucleated hematopoietic (leukocyte) cells. CD45/LCA regulates antigen‑receptor signaling, exists in multiple isoforms, and is widely used as a pan‑leukocyte immunohistochemical marker to identify and classify hematologic cells and lymphoid malignancies.

CD45 (leukocyte common antigen) is a pan‑leukocyte marker used to identify hematopoietic/lymphoid cells and aids lymphoma diagnosis. Most B‑ and T‑cell lymphomas express CD45, but expression may be reduced or absent in certain entities (for example classical Hodgkin lymphoma Reed–Sternberg cells and some plasma‑cell variants). Flow cytometry and immunohistochemistry use CD45 alongside other markers for accurate classification.

A CD45‑positive result means the cells express CD45 (the leukocyte common antigen), indicating they are of hematopoietic/white‑blood‑cell origin. It’s used in flow cytometry and immunohistochemistry to identify and classify leukocytes and to help distinguish lymphoid or myeloid malignancies from non‑hematopoietic tumors. Most leukocytes are CD45+, while mature red cells and platelets lack CD45.

CD45 is not a general tumor marker. It’s a pan‑leukocyte (leukocyte common antigen) surface protein used to identify hematopoietic cells and distinguish blood‑cell–derived malignancies (leukemias, lymphomas) from non‑hematologic tumors. Some hematologic cancers show altered CD45 expression, so it aids diagnosis and classification, but it is not a tumor‑specific marker for solid tumors or a universal cancer biomarker.

CD45 is the pan‑leukocyte marker; a “normal” CD45+ cell count generally mirrors the normal white blood cell count: about 4.0–11.0 × 10^9/L (4,000–11,000/µL). Flow cytometry reports CD45 expression patterns (intensity and percentage) rather than a single universal cutoff; laboratory-specific reference ranges, complete blood count values and clinical context determine whether a result is normal.