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Hairy cell leukemia-associated antigen LeuM5 (CD11c) is preferentially expressed by benign activated and neoplastic
A Chadburn1, G Inghirami, D M Knowles
1Department of Pathology Columbia University College of Physicians and Surgeons, New York, NY 10032.
Insights
LeuM5 antigen expression is linked to T-cell activation, particularly in CD8 cells. This marker is also found in a subset of T-cell neoplasms, especially those with a CD4-CD8+ phenotype.
Area of Science:
- Immunology
- Cell Biology
Background:
- LeuM5 antigen (CD11c, p150.95) is an established immunodiagnostic marker for B-cell hairy cell leukemia.
- Its expression on T cells, particularly in the context of activation and neoplasms, requires further elucidation.
Purpose of the Study:
- To investigate LeuM5 antigen expression on normal peripheral blood T cells following in vitro activation.
- To analyze LeuM5 expression across a diverse panel of T-cell neoplasms.
Main Methods:
- Flow cytometry was used to assess LeuM5 expression on resting and phytohemagglutinin-stimulated normal T cells.
- Two-color flow cytometry analyzed LeuM5 expression in relation to CD4 and CD8 markers on activated T cells and T-cell neoplasms.
Main Results:
- Resting T cells did not express LeuM5; expression emerged after 3-4 days of in vitro activation and persisted on the cell surface.
- Activated T cells showed preferential LeuM5 expression on CD8+ cells (mean 44%) compared to CD4+ cells (mean 12%).
- LeuM5 was detected on a variable proportion of neoplastic T cells (26%), notably in CD4-CD8+ T-cell neoplasms (67%).
Conclusions:
- LeuM5 antigen expression is associated with T-cell activation.
- The LeuM5 antigen is preferentially expressed by activated CD8+ T cells.
- Variable LeuM5 expression occurs in T-cell neoplasms, particularly those with a CD4-CD8+ phenotype, suggesting potential diagnostic utility.
Abstract:
LeuM5 antigen (CD11c, p150.95) expression, widely used as an immunodiagnostic marker for B-cell hairy cell leukemia, was examined on benign, normal peripheral blood T cells before and after stimulation in vitro with phytohemagglutinin and on a large, diverse panel of 73 T-cell neoplasms. Resting T cells lacked LeuM5. Intracytoplasmic LeuM5 was detectable at 3 to 4 days and surface membrane LeuM5 was detectable continuously between 5 and 17 days on greater than or equal to 20% CD3 cells (maximum, 42% CD3 cells at 10 days) after activation. Two-color flow cytometric analysis of the activated T cells demonstrated that a maximum of 60% CD8 but only 25% CD4 cells expressed LeuM5; the mean percentage of LeuM5+ CD8 cells was 44% compared with 12% LeuM5+ CD4 cells. A variable proportion of the neoplastic T cells in 19 of 73 (26%) T-cell neoplasms were LeuM5+. Twelve of 18 CD4-CD8+ (67%) but only 5 of 40 CD4+ CD8- T-cell neoplasms expressed LeuM5. These studies demonstrate that the LeuM5 antigen is 1) expressed in association with T-cell activation, 2) preferentially expressed by activated CD8 cells, and 3) variably expressed by neoplastic T cells, but particularly by those exhibiting the CD4- CD8+ phenotype.
