TCRγδ

Summary

In the detection of haematological malignancy the purpose of detecting γδ T cells is to define particular T cell lymphomas (αβ T cells strongly predominate in normal blood). However care must be taken when small populations of γδ T cells are detected however, since these may arise in response to viral or other immune responses.

Background

T cell receptor (TCR) analysis in blood is not generally helpful in indicating T-cell clonality since around 95% express of circulating T cells express αβ chains and only 5% have gamma γδ. In tissues this can be different since the γδ T cells are more abundant in skin and intraepithelial areas. The receptors also have different functions: αβ T cells behave as elements of the adaptive immune system while γδ cells have an innate immune function similar to NK cells.

Diagnostic Use

• A predominant population of γδ T cells circulate may indicate a clonal proliferation most commonly will be hepatosplenic gamma-delta T-cell lymphoma or primary cutaneous t cell lymphoma (PTCL)
• Disturbance of the ratio of αβ/γδ may be seen in reactive conditions

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