CD45 (leukocyte common antigen, LCA)

There are at least five proteins in the CD 45 family. They are tyrosine phosphatases present on the surface of almost all haematolymphoid cells. The information below relates to LCA: antibodies which recognise all isoforms of CD 45. See also the restricted isoforms CD 45RA and CD 45RO

Antibodies are effective on paraffin-embedded tissue1. It is common to use a cocktail of monoclonal antibodies, such as 2B11 and PD7/26, each of which recognises different epitopes.

Immunohistochemical expression

• almost all haematolymphoid cells:

  • T lymphocytes

  • B lymphocytes

  • granulocytes

  • monocytes

  • macrophages

  • not maturing erythrocytes and megakaryocytes

• 93% to 99% of all lymphomas. Positivity is seen in 97% of B-cell, 90% of T-cell lymphomas and 69% of precursor B and T lymphoblastic lymphomas. Occasional high grade lymphomas are CD45- / CD20+.

• Reed-Sternberg cells in Hodgkin's disease, lymphocyte predominant subtype. The RS cells of classical Hodgkin lymphoma are usually negative.

• 50-87% of anaplastic large cell lymphomas

• some plasmacytomas / myelomas

• hairy cell leukaemia

• all T cell ALL

• 80% of B cell ALL

• Langerhan's cell histiocytosis

• true histiocytic tumours are negative

• rarely positive in rhabdomyosarcomas

Diagnostic utility

• A first line marker for the identification of lymphomas

References

1 Leong A S-Y, Cooper K and Leong FJ W-M. Manual of diagnostic antibodies for immunohistology. 2nd edition, 2003

©SMUHT/PW Bishop