T cell Interleukin Proliferation
Utility: Functional evaluation of T cell proliferation to interleukins.
Specimen: 8 - 15 mL peripheral blood in sodium heparin (green top).
CPT codes: 86353 x 5, 88187.
Clinical indication/general description
Once a defect in T cells is detected, or defective T cell function is suspected, further evaluation involves examination of T cell proliferation in response to interleukins. Activation of T cells with antibodies to the T cell receptor and cytokines results in the proliferation of T cells over the next seven to 10 days. Diminished or absent proliferative response to T cell stimuli is consistent with a primary (such as severe combined immunodeficiency) or secondary immunodeficiency disease that affects T lymphocytes (cellular immunity). This assay tests the proliferative function of T cells in response to cytokines and a variety of growth factors to help determine if defective proliferation is the result of defective growth factor secretion or defective growth factor receptor expression. This assay is designed to be used only if the T mitogen assay is abnormal (see below).
A functional flow cytometric-based assay provides a semi-quantitative assessment of lymphocyte proliferation to CD3/IL-2, CD3/IL-7, CD3/IL-15 and CD3/CD28. Lymphocytes are labeled with the fluorescent proliferation tracking dye CFSE and activated with cytokines. As lymphocytes divide, the fluorescent label is diluted in half, which can be seen on flow diagrams as peaks of decreasing fluorescence. Lymphocyte proliferative response is demonstrated by an increase in FSC/SSC and a progressive two-fold reduction in the proliferation tracking dye.