Test Catalog

Test ID: CD4I    
CD4 Immunostain, Technical Component Only

Useful For Suggests clinical disorders or settings where the test may be helpful

Identification of T helper cells, histiocytes, and monocytes

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

CD4 (cluster of differentiation 4) is expressed on a subset of T cells (T helper cells), histiocytes, and monocytes. In normal tonsil, the T cells predominate in interfollicular regions. This immunostain is also used to support T cell or histiocytic lineage in hematolymphoid neoplasms.

Interpretation Provides information to assist in interpretation of the test results

This test does not include pathologist interpretation; only technical performance of the stain. If interpretation is required order PATHC / Pathology Consultation for a full diagnostic evaluation or second opinion of the case.


The positive and negative controls are verified as showing appropriate immunoreactivity and documentation is retained at Mayo Clinic Rochester. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request. Contact 855-516-8404.


Interpretation of this test should be performed in the context of the patient's clinical history and other diagnostic tests by a qualified pathologist.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Age of a cut paraffin section can affect immunoreactivity. Stability thresholds vary widely among published literature and are antigen-dependent. Best practice is for paraffin sections to be cut within 6 weeks.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Kristensen LK, Frohlich C, Christensen C, et al: CD4(+) and CD8a (+) PET imaging predicts response to novel PD-1 checkpoint inhibitor: studies of Sym021 in syngeneic mouse cancer models. Theranostics. 2019 Oct 18;9(26):8221-8238. doi: 10.7150/thno.37513

2. Prat A, Navarro A, Pare L, et al: Immune-related gene expression profiling after PD-1 blockade in non-small cell lung carcinoma, head and neck squamous cell carcinoma, and melanoma. Cancer Res. 2017 Jul 1;77(13):3540-3550. doi: 10.1158/0008-5472.CAN-16-3556
3. Sharma A, Subudhi SK, Blando J, et al: Anti-CTLA-4 immunotherapy does not deplete FOXP3(+) regulatory T cells (Tregs) in human cancers. Clin Cancer Res. 2019 Feb 15;25(4):1233-1238. doi: 10.1158/1078-0432.CCR-18-0762