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Cytokine expression by high-density human lymphocytes
W A Sewell1, M F Berger, L J Skipsey
1Center for Immunology, University of New South Wales, Sydney, Australia.
Insights
Resting T lymphocytes, purified by high density, show specific cytokine expression patterns. These cells can acquire broader inducible cytokine expression, including IL-5, after activation and restimulation.
Area of Science:
- Immunology
- Cell Biology
Background:
- T lymphocytes exist primarily as quiescent, non-cycling cells.
- Understanding cytokine expression in resting T cells is crucial for immune response studies.
Purpose of the Study:
- To investigate cytokine mRNA expression patterns in high-density, resting human T lymphocytes.
- To determine the potential of these resting cells to develop broader cytokine expression upon activation.
Main Methods:
- Purification of high-density T lymphocytes from human peripheral blood mononuclear cells (PBMC).
- Assessment of cytokine mRNA expression (IL-2, IL-3, IFN-gamma, IL-4, IL-5) using reverse transcription-polymerase chain reaction (RT-PCR).
- Analysis of cytokine expression in relation to CD45RO marker and after in vitro activation and restimulation.
Main Results:
- High-density lymphocytes exhibited similar IL-2, IL-3, and IFN-gamma expression compared to unfractionated PBMC.
- Reduced IL-4 and minimal IL-5 expression were observed in high-density lymphocytes.
- IFN-gamma was primarily in CD45RO+ cells, while IL-2 was in both CD45RO+ and CD45RO- subsets.
- Both CD45RO+ and CD45RO- derived cells expressed IL-5 after restimulation, indicating acquired potential.
Conclusions:
- High-density T lymphocytes possess a distinct baseline cytokine profile.
- These resting T cells retain the capacity to develop broader inducible cytokine expression, including IL-5, following activation.
- The CD45RO marker does not solely dictate IL-4 and IL-5 inducibility in resting cells.
Abstract:
T lymphocytes spend much of the time as small non-cycling cells. To determine the pattern of cytokine expression in such resting cells, they were purified from human peripheral blood mononuclear cells (PBMC) on the basis of high buoyant density. The cells were stimulated and cytokine mRNA expression was assessed by reverse transcription-polymerase chain reaction (RT-PCR). Expression of interleukin-2 (IL-2), IL-3 and interferon-gamma (IFN-gamma) was similar in high-density lymphocytes and in unfractionated PBMC. In contrast, the high-density lymphocytes expressed less IL-4 than PBMC, and little or no IL-5. Because a substantial minority of the high-density lymphocytes was CD45RO+, the presence of this marker was not an indicator of the ability to express IL-4 and IL-5. In the high-density lymphocytes, IFN-gamma expression was confined to the CD45RO+ fraction, whereas IL-2 was expressed by both CD45RO+ and CD45RO- subsets. To assess whether high-density lymphocytes could give rise to cells with a broader range of inducible cytokine expression, they were activated and then restimulated between 10 and 22 days of culture. Cells derived from both the CD45RO+ and CD45RO- fractions of high-density lymphocytes expressed IL-5 after restimulation. Thus the high-density lymphocyte population has the potential to acquire a broader range of inducible cytokine expression.
