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Evidence for excessive Th2 CD4+ subset activity in vivo
E H Field1, R J Noelle, T Rouse
1Department of Medicine, University of Iowa College of Medicine, Iowa City 52242.
Insights
This study provides evidence that T helper 2 (Th2) cells exist and function in vivo. An expanded Th2 cell population in a patient produced excessive cytokines, potentially contributing to sinopulmonary pathology.
Area of Science:
- Immunology
- Cellular Biology
- Molecular Medicine
Background:
- The in vivo existence and function of distinct T helper 1 (Th1) and T helper 2 (Th2) CD4+ T cell subsets remain debated.
- Understanding in vivo T cell subset function is crucial for diagnosing and treating immune-mediated diseases.
Observation:
- A patient presented with laboratory findings suggestive of high T helper 2 (Th2) cell activity, including elevated IgG4, IgE, and eosinophilia.
- Patient peripheral blood lymphocytes (PBL) induced heightened IgG4 and IgE production in normal B cells, indicating T cell-driven immunoglobulin production.
- Flow cytometry and RNA in situ hybridization revealed an expanded CD4+Leu-8+CD45RA- memory-effector T cell population in the patient, enriched for interleukin-4 (IL-4) transcription.
Findings:
- Activated patient PBL secreted significantly higher levels of IL-4 and IL-5, and lower levels of IL-2, compared to controls, with similar interferon-gamma (IFN-γ) levels.
- Semiquantitative reverse polymerase chain reaction confirmed increased IL-4 and IL-5 mRNA expression in patient PBL.
- The expanded CD4+Leu-8+CD45RA- population showed a 2:1 ratio of IL-4-transcribing to IFN-γ-transcribing cells, confirming the in vivo presence of functional Th2 cells.
Implications:
- These findings provide strong evidence for the in vivo existence and functional activity of Th2 cells.
- The expanded Th2 cell population and its excessive cytokine production may contribute to the patient's sinopulmonary pathology.
- This study advances our understanding of T cell subset dynamics in human disease and has potential implications for targeted immunotherapies.
Abstract:
Although distinct Th1 and Th2 CD4+ subsets are apparent in in vitro studies, controversy exists over whether these subsets occur functionally in vivo. We describe a patient whose presenting laboratory features of elevated IgG4 and IgE and eosinophilia suggested high levels of IL-4 and IL-5 and in vivo expansion of the CD4+ Th2 subset. Anti-CD3-activated patient PBL induced heightened levels of IgG4 and IgE from normal B cells, indicating that the patient's abnormal Ig isotypes were T cell driven. Stimulated PBL from the patient secreted more IL-4, compared with control PBL, but similar levels of IFN-gamma. Semiquantitative reverse polymerase chain reaction demonstrated that activated PBL from the patient produced higher IL-4 and IL-5, lower IL-2, and similar IFN-gamma mRNA levels, compared with controls. FACS analysis showed that the patient expressed an expanded population of CD4+Leu-8+CD45RA- cells, the memory-effector population, and RNA in situ hybridization confirmed that the CD4+Leu-8+CD45RA- population of the patient was enriched for IL-4-transcribing cells. Moreover, IL-4-transcribing cells outnumbered IFN-gamma-transcribing cells by 2:1 in the memory-effector CD4 population, confirming that Th2 cells exist in vivo within the expanded CD4+Leu-8+CD45RA- population. Taken together, these results provide evidence that Th2 cells exist in vivo and they suggest that the expanded Th2 population produces excessive cytokines that may contribute to the sinopulmonary pathology of the patient.