Which cell type is CD2 (Cluster of Differentiation 2) positive in?

CD2 Expression in Lymphocyte Populations

CD2 is positive in T cells, as it is a cell surface glycoprotein expressed on virtually all mature T lymphocytes and natural killer (NK) cells, but not on B cells or hematopoietic stem cells. 1

CD2 Expression Pattern in Different Cell Types

CD2 (also known as LFA-2) is a key T-cell surface marker with well-defined expression patterns:

• T cells: CD2 is expressed on virtually all mature T cells and is considered a pan-T cell marker alongside CD3, CD5, and CD7 1, 2

• NK cells: CD2 is also expressed on most natural killer cells 3

• B cells: CD2 is not expressed on B cells (CD19+, CD20+, CD79a+, PAX5+ cells) 1

• Precursor B cells: CD2 is not expressed on precursor B cells 1

• Hematopoietic stem cells (HSCs): CD2 is not expressed on HSCs 1

Functional Significance of CD2

CD2 serves two critical functions in T cell biology:

1. Cell adhesion: CD2 functions as an adhesion molecule by binding to its ligand LFA-3 (CD58), which is expressed on antigen-presenting cells. This interaction facilitates the formation of the immunological synapse between T cells and antigen-presenting cells 4, 3

2. T cell activation: CD2 participates in signal transduction and can function as a costimulatory molecule for T cell activation 3

Clinical Relevance

Understanding CD2 expression is important for:

• Immunophenotyping: CD2 is used in flow cytometry panels to identify T cells and NK cells, particularly in the diagnosis of T-cell lymphomas and leukemias 2

• T-cell large granular lymphocyte leukemia (LGLL-T): Diagnosis includes assessment of CD2 expression alongside other T-cell markers 2

• Therapeutic targeting: CD2 is an attractive target for monoclonal antibodies intended for treatment of conditions characterized by undesired T cell activation 3

Common Pitfalls in CD2 Assessment

• When performing flow cytometry for T-cell evaluation, it's important to include CD2 in panels with other T-cell markers (CD3, CD5, CD7) for comprehensive assessment 2

• Interpretation of CD2 expression should be done in the context of other markers, as CD2 alone is not sufficient to definitively identify T cells 1

• In some T-cell malignancies, CD2 expression may be preserved even when other T-cell markers are lost, making it a valuable diagnostic marker 2

In summary, CD2 is a characteristic marker of T cells and NK cells, but is not expressed on B cells, precursor B cells, or hematopoietic stem cells.