Covid, thyme ‘shield’ against long-term lung damage, Italian study

The thymus, a key gland in the immune system, protects the lungs from long-term damage from Covid. Its ‘shield effect’ was revealed by an Italian study conducted by a group of researchers from the Italian Diagnostic Center (Cdi) and the Fatebenefratelli hospital of the Asst Fbf Sacco in Milan, published in ‘Applied Sciences’.

The thymus – explain the CDI – is a gland located in the chest in a retrosternal position, which plays a fundamental role in the maturation of T lymphocytes of the immune system. After puberty, its size and activity normally decrease and the thymus is progressively replaced by adipose tissue, a transformation that is more evident in females. This reduction in size makes the thymus less distinguishable in computed tomography (CT) images. The thymus, however, can swell again and reactivate in response to autoimmune diseases or a viral infection such as Sars-CoV-2, to increase the production of T lymphocytes and strengthen the immune defenses. Previous research had already indicated that a reactivated or enlarged thymus is associated with a better prognosis in the acute phases of Sars-CoV-2 disease, but the new work suggests “a protective role of the gland even over a longer period and opens up new research perspectives on its function in combating viral infections”.

The scientists observed that “a well-visible thymus in CT images collected 3 months after hospital discharge for Covid-19 is accompanied by a better state of health of the lungs of previously hospitalized patients. In particular, in subjects who, on radiological examination, showed a thymus not yet replaced by fat, zero or slight alterations of the lung tissue were observed. Conversely, subjects in whom the thymus was progressively replaced by fat, and therefore less and less distinguishable in radiological images, showed moderate to severe alterations of the lung tissue”.

“This research work – says Deborah Fazzini, director of Up Diagnostic Imaging and Stereotactic Radiosurgery, Cdi – was born from an intuition I had during radiological observation: I noticed frequent and unusual activations of the thymus in this type of patient, especially in women, in whom the gland is generally less visible. Where the thymus was evident, there were fewer pulmonary sequelae after Covid-19 infection”.

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“To validate this hypothesis – the specialist reports – we analyzed the appearance of the thymus through chest CT in 102 adult patients previously hospitalized for Covid-19, followed with a control CT 3 months after discharge. The results obtained support the hypothesis that thymus reactivation plays an important protective role, offering new perspectives on the immune dynamics linked to the coronavirus and indicating the thymus as a key factor in resilience to post-infection pulmonary complications”.