CD7, also known as GP40, is a transmembrane glycoprotein and a member of the immunoglobulin superfamily, primarily expressed on the surface of T cells and natural killer （NK） cells. It is highly expressed in acute T-cell leukemia （T-ALL） and certain peripheral T-cell lymphomas. CD7 plays a significant role in the regulation and activation of the immune system. It is involved in T-cell and T-cell/B-cell interactions during early lymphoid development and acts as a co-stimulatory molecule with CD3, CD45, and PI3K. CD7 has two known ligands, K12 protein and galectin-1, which can influence T cell proliferation, migration, and apoptosis. Additionally, CD7 is being explored as a target for cancer therapies, such as antibody-drug conjugates, due to its high expression in certain malignancies.