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IL-8 gene expression and production in human peripheral blood lymphocyte subsets
M J Smyth1, C O Zachariae, Y Norihisa
1Laboratory of Experimental Immunology, NCI-FCRDC, Frederick, MD 21702-1201.
Abstract:
We have investigated IL-8 mRNA expression and IL-8 production in highly purified subsets of peripheral blood lymphocytes. T cells stimulated with PHA, ionomycin, or PMA alone failed to express IL-8 mRNA. However T cells stimulated with a combination of PMA and ionomycin or PMA and PHA expressed IL-8 mRNA in a PMA dose-dependent manner and maximally after 3 to 6 h of culture. Induction of IL-8 mRNA appeared to be specifically in the CD4+ T cell subset. Surprisingly, however, T cells were not induced to secrete significant levels of IL-8 polypeptide, even in the presence of accessory monocytes. In addition, immunoprecipitation analysis of PMA/ionomycin-treated T cell lysates detected only minor levels of cellular IL-8 Ag thereby suggesting that in T cells, the production of IL-8 was inhibited at the posttranscriptional level. By contrast, CD3- large granular lymphocytes (LGL) were both induced to express IL-8 mRNA and secrete biologically active IL-8 upon specific stimulation with IL-2 and ligand (anti-CD16 mAb) for the NK cell receptor for IgG-Fc (CD16), or upon nonspecific stimulation with PMA. IL-2 and anti-CD16 mAb synergistically induced IL-8 expression in LGL. Other nonactivating LGL-specific mAb did not induce LGL IL-8 secretion. The amount of IL-8 produced by activated LGL was donor variable, but generally 5 to 10 times less than that secreted by monocytes. The ability of LGL to release IL-8 and a large number of other cytokines further supports the hypothesis that LGL may contribute to both inflammatory and immunologic responses.
Insights
Interleukin-8 (IL-8) mRNA is induced in T cells, but not significantly produced. Large granular lymphocytes (LGLs) express IL-8 mRNA and secrete IL-8, suggesting a role in immune responses.
Area of Science:
- Immunology
- Molecular Biology
Background:
- Interleukin-8 (IL-8) is a key cytokine involved in inflammatory and immune responses.
- Understanding IL-8 regulation in different lymphocyte subsets is crucial for deciphering immune cell functions.
Purpose of the Study:
- To investigate the expression and production of IL-8 mRNA and protein in purified human peripheral blood lymphocyte subsets.
- To determine the regulatory mechanisms of IL-8 expression in T cells and large granular lymphocytes (LGLs).
Main Methods:
- Purification of peripheral blood lymphocyte subsets (T cells, CD4+ T cells, CD3- LGLs).
- Stimulation of lymphocytes with various agents (PHA, ionomycin, PMA, IL-2, anti-CD16 mAb).
- Analysis of IL-8 mRNA expression (Northern blot or similar) and protein production (ELISA, immunoprecipitation).
Main Results:
- T cells, particularly CD4+ T cells, expressed IL-8 mRNA upon stimulation with PMA/ionomycin or PMA/PHA, but showed minimal IL-8 protein secretion, indicating post-transcriptional inhibition.
- CD3- LGLs expressed IL-8 mRNA and secreted biologically active IL-8 upon stimulation with IL-2/anti-CD16 mAb or PMA.
- IL-2 and anti-CD16 mAb synergistically induced IL-8 expression in LGLs, with production levels generally lower than monocytes.
Conclusions:
- T cells exhibit post-transcriptional regulation of IL-8 production.
- LGLs are a significant source of IL-8, contributing to inflammatory and immunologic responses.
- LGLs' cytokine-releasing capacity highlights their role in modulating immune activity.