The yin and the yang of immunosuppression with inhaled corticosteroids
- 1Academic Unit of Respiratory Medicine, University of Sheffield, Sheffield, UK
- 2Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
- 3Department of Pulmonology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
- 4Laboratory of Allergology & Pulmonary Diseases, GRIAC Research Institute, University Medical Center Groningen, Groningen, The Netherlands
- 5Laboratory of Allergology & Pulmonary Diseases, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
- 6Academic Unit of Immunology and Infectious Diseases, Department of Infection and Immunity, University of Sheffield, Sheffield, UK
- Correspondence to Professor Ian Sabroe, Academic Unit of Respiratory Medicine, Medical School, University of Sheffield, Beech Hill Road, Sheffield S10 2RX, UK;
A patient who is immunosuppressed is susceptible to mycobacterial infection: are you surprised? Before you jump to conclusions, you might wish to clarify the nature and extent of immunosuppression, and whether it is through disease, therapy, or both, reserving judgement until you know more.
Patients are often concerned about immunosuppressive effects of inhaled and oral corticosteroids. Asthmatics are used to infections putting them in hospital, and not unreasonably view with suspicion any treatment option that might make this more likely to happen. However, healthcare providers know that for asthmatics, appropriate local immunomodulation in the lung with inhaled corticosteroids (ICS) is associated with decreased exacerbations arising from viral infections, fewer symptoms, improved lung function and better outcomes. In subsets of patients with COPD, high-dose fluticasone with salmeterol reduces exacerbations and improves quality of life.1 Thus, if the only exposure of patients to anything remotely immunosuppressive is ICS, you might conclude the extent of immunosuppression is insufficient to regard the patient as immunocompromised.
But will use of ICS increase susceptibility to some infections? The innate immune networks active in the lung, with their multifaceted humoral and cellular components, show intrinsic competence in keeping the human organism mostly free of serious pulmonary infection. At their heart lie strong surface barriers, an effective mechanism of sensing pathogens through a range of pattern recognition receptors,2 the efficient killing of micro-organisms by resident and recruited phagocytes, and efficient resolution of inflammation.3 Alveolar macrophages are the resident phagocytes, which along with epithelial cells and T cells coordinate an immune response that may require recruitment of other inflammatory cells such as neutrophils to clear invading pathogens. Clearance of bacteria such as pneumococci relies heavily on phagocyte competence which is optimised by T cell responses. When phagocyte capacity is stressed by intracellular pathogens, such as Mycobacterium …