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Th17 cells: a new T lymphocyte and its roll in asthma.

The numbers of specific T cell lymphocytes have had an important addition - the Th17 regulator. The expanding T cell lymphocyte family include; Th1, aimed at intracellular pathogens such as viral infections, Th2 offers some protection against worms and is associated with allergy, Th 3 a regulator and now Th17 a regulator that can also act to help clear up fungi and bacterial infection through the activation of neutrophils. Neutrophil activity in asthma can exist along side 'allergic IgE' asthma.

Regarding Th17 roll in clearing up fungi it is important to note that fungal hyphae, able to survive the toxic gut of house dust mites, have been photographed growing out the mite's droppings, and that Th 17 helps to clear up fungi thorough neutrophil products. As the authors report, 'It is well known that steroid treatments have little effect in neutrophilic asthma, whereas they work fine in eosinophilic [allergic] asthma...'. In 'difficult-to-control (steroid-resistant) asthma this may be important.

This review paper not only describes each T lymphocyte's responsibility, and the defence mechanisms they produce, but how they can also cause disease including allergy and are involved in some autoimmune diseases. The paper speculates on a fourth T lymphocyte as indicated in research. This 'phantom' lymphocyte appears as a combination of Th2/Th17, possibly a marker of sensitisation or in severe asthma. The major mite allergen Der p1- was referred to in this speculation. Confirmation is needed on Th2/Th17 existence.

Interesting quote from the paper, ' The main role of Th17 is their ability to recruit and activate neutrophil granulocytes, either directly through IL-8 production or indirectly by inducing the production of colony stimulatory factors (CSF) or CXCL8 by tissue resident cells.'

References

'Th 17 cells: new players in asthma pathogenesis', Cosmi L, Liotta F, Maggi E, Romagnani S, Annunziato, Allergy, 2011: John Wiley and Sons A/S DOI: 10.111/j.1398-9995.2011.02576.x.

'Dust Mites', Colloff M.J.(2009) CSIRO Publishing. Page 54

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