CD4+ T effector lymphocytes are classified in different subsets on the basis of cytokine secretion:
- Th1 cells, thank to IFN-γ production, are responsible for cell-mediated immunity against intracellular pathogens
- Th2 cells, through the production of IL-4, provide protection against helminthes
- Th17 cells, via IL-17, promote neutrophils recruitment for the clearance of bacteria and fungi
T helper cells (click to enlarge the image).
However, beyond their protective role, T-helpers can also be involved in inflammatory diseases such as asthma.
Allergic asthma is the result of an inflammatory process driven by allergen-specific Th2 lymphocytes.
On the other hand, Th17 cells are mainly involved in those forms of asthma, where neutrophils more than eosinophils, contribute to the inflammation.
The identification of Th17/Th2 cells, able to produce both IL-4 and IL-17, fits the observation that different clinical phenotypes can coexist in the same patient.
Cosmi L, Liotta F, Maggi E, Romagnani S, Annunziato F. Th17 cells: new players in asthma pathogenesis. Allergy 2011; DOI: 10.1111/j.1398-9995.2011.02576.x.
Anti-IL-17 Receptor Antibody Brodalumab Helps Patients with Psoriasis - NEJM, 2012.
Anti–Interleukin-17 Monoclonal Antibody Ixekizumab Improves Chronic Plaque Psoriasis - NEJM, 2012.
T Helper Cells