Written by Dr Fasihul Khan, Consultant Respiratory Physician and ILD specialist, providing expert guidance on interstitial lung disease.
Key points
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Immunosuppressive treatment is used when inflammation is driving lung disease
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It is commonly used in autoimmune-related ILD
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It is not routinely used in idiopathic pulmonary fibrosis (IPF)
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The presence of fibrosis alone does not mean immunosuppression will help
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Treatment decisions depend on disease pattern, behaviour, and clinical context
Inflammation and fibrosis: two different processes
Interstitial lung disease encompasses a broad group of conditions. In some, inflammation is the dominant process. In others, established fibrosis (scarring) predominates. Many patients have elements of both, but the relative contribution of each determines treatment strategy.
Inflammatory ILD involves immune-mediated injury to the lung tissue. In this setting, immunosuppressive therapy may reduce on-going damage and limit progression. When fibrosis becomes established, however, scar tissue cannot be reversed by suppressing the immune system. At that stage, treatment decisions shift toward stabilising disease rather than reversing injury. This distinction explains why immunosuppression may be appropriate in some patients but avoided in others.
When is immunosuppression appropriate?
Immunosuppressive therapy is most commonly used in interstitial lung disease associated with autoimmune or connective tissue disorders. Conditions such as rheumatoid arthritis, systemic sclerosis, inflammatory myositis, mixed connective tissue disease, and lupus can all involve the lungs as part of systemic immune dysregulation. In these settings, medications such as prednisolone, mycophenolate mofetil, azathioprine, cyclophosphamide, or biologic agents like rituximab may be used to reduce immune-driven lung injury. The aim is to suppress active inflammation, stabilise lung function, and reduce the risk of further fibrosis developing.
Immunosuppression may also be considered in selected cases of fibrotic hypersensitivity pneumonitis when inflammatory activity persists despite environmental antigen avoidance. Importantly, treatment is not based solely on diagnosis. It is guided by imaging features, lung function trends, blood test results, systemic symptoms, and disease trajectory over time.
In contrast, immunosuppressive therapy is not recommended as standard treatment in idiopathic pulmonary fibrosis. Clinical trials have shown harm with certain immunosuppressive combinations in IPF, and current international guidance advises against routine use in this condition. Similarly, in patients with predominantly established fibrosis and little evidence of on-going inflammatory activity, immunosuppression may offer limited benefit while exposing patients to avoidable risk. The presence of fibrosis on CT does not automatically mean the immune system is actively driving disease. Treatment must align with biology rather than imaging terminology alone.
Where does prednisolone fit in?
Prednisolone (a corticosteroid) is often used in ILD when inflammation is suspected, particularly if symptoms are changing quickly, imaging suggests active inflammatory change, or there is an autoimmune flare. Steroids act more rapidly than most other immunosuppressive medications and are therefore sometimes used as an initial treatment or short-term “bridge” while longer-acting steroid-sparing therapy (such as mycophenolate) takes effect.
However, long-term prednisolone is avoided where possible because side-effects accumulate with duration and dose. The aim is usually to use the lowest effective dose for the shortest necessary period, with a clear tapering strategy. In idiopathic pulmonary fibrosis and other predominantly fibrotic disease without evidence of active inflammation, routine steroid treatment is not recommended and may expose patients to unnecessary risk.
What benefit can patients expect and what are the risks?
When immunosuppression is appropriate, the goal is to reduce active inflammation and stabilise lung function. In some cases, particularly when treatment is initiated early and inflammation is prominent, measurable improvement in lung function may occur. More commonly, the aim is stabilisation rather than reversal. Response is assessed longitudinally. Serial lung function testing, symptom review, and imaging comparison help determine whether treatment is achieving its intended effect. As with most ILD therapies, the benefit of immunosuppression becomes clearer over months rather than days.
Immunosuppressive medications do not “switch off” the immune system completely. Instead, they reduce over activity in a controlled way. However, because immune activity is dampened, infection risk increases. Blood count abnormalities, liver enzyme changes, and gastrointestinal side-effects can also occur depending on the specific medication used, and long-term risks vary between agents. Corticosteroids such as prednisolone may also cause weight gain, mood disturbance, sleep disruption, raised blood pressure, raised blood sugar, osteoporosis, and increased infection susceptibility, particularly with prolonged use.
For this reason, monitoring is structured and proactive. Blood tests are performed regularly, particularly early in treatment, vaccination status is reviewed, and patients are advised when to seek medical attention. The decision to initiate immunosuppression balances potential benefit against these risks. Age, comorbidities, prior infection history, and overall frailty all influence this assessment.
Can immunosuppression and anti-fibrotic therapy be combined?
In selected patients, yes. Some connective tissue disease-associated ILDs demonstrate progressive fibrosis despite immunosuppression. In these cases, anti-fibrotic therapy may be introduced alongside on-going immunomodulatory treatment. This reflects the reality that inflammation and fibrosis can coexist, and disease behaviour may evolve over time. Combining therapies requires careful specialist oversight. The decision is guided by longitudinal assessment, not by diagnosis alone.
How is the treatment decision made?
The choice to initiate immunosuppression is rarely based on a single test or scan. It typically follows multidisciplinary discussion, incorporating radiological interpretation, physiological trends, autoimmune evaluation, and systemic clinical features. Radiological patterns suggesting inflammatory activity, elevated autoimmune markers, systemic manifestations of connective tissue disease, or a sub-acute presentation may all support immunosuppressive therapy. Conversely, extensive honeycombing, a clear idiopathic pulmonary fibrosis phenotype, or long-standing stable fibrosis without inflammatory features may argue against it.
Starting immunosuppression does not necessarily mean disease is “severe”. In inflammatory ILD it may be introduced early to prevent progression, even when lung function is relatively preserved. Conversely, advanced fibrosis without active inflammation may not benefit from immune suppression. Severity and treatment are not always directly aligned; biology and trajectory matter more than a single number.
When is specialist review particularly valuable?
Specialist ILD review is particularly helpful when the distinction between inflammatory and fibrotic disease is unclear, when imaging features are mixed, when lung function trends are evolving, or when response to treatment is uncertain.
Because immunosuppression carries meaningful risk, careful patient selection is essential. Equally, withholding immunosuppression in predominantly inflammatory ILD may allow avoidable progression. Borderline cases are common. This is where nuance and experience become essential. ILD management often involves interpreting patterns rather than applying rigid algorithms.
Structured, longitudinal assessment ensures that treatment decisions reflect disease behaviour rather than terminology alone.