Stroke is a leading cause of disability worldwide with a high mortality rate. It is a medical emergency that occurs when the blood supply to the brain is interrupted or reduced, leading to the damage or death of brain cells.

The immune system is crucial in restoring the damaged cells and tissues following a stroke. However, recent studies have shown that stroke can lead to a state of immune suppression, which can further exacerbate the damage caused by stroke.

What is Immune Suppression?

Immune suppression, also known as immune dysfunction or immune paralysis, is a state in which the immune system becomes less responsive or inactive.

It is a common phenomenon that occurs after major trauma or severe infections, as the body tries to limit the collateral damage caused by an overactive immune system. However, immune suppression following a stroke is a unique phenomenon as it affects the brain and can lead to long-term disability.

What Causes Immune Suppression following Stroke?

The exact mechanisms that lead to immune suppression following stroke are not well understood.

However, it is believed that the immune system is activated in response to the injury caused by stroke, leading to the production of pro-inflammatory cytokines and other immune cells. This initial immune response is critical in eliminating the damaged tissues and restoring the brain function.

However, it is also associated with the activation of the hypothalamic-pituitary-adrenal axis, which can lead to the secretion of glucocorticoids, such as cortisol, and other stress hormones. These hormones can suppress the immune response and lead to immune dysfunction.

Another mechanism that may contribute to immune suppression following stroke is the activation of the sympathetic nervous system, which can increase the levels of the neurotransmitter norepinephrine.

Norepinephrine can inhibit the production of pro-inflammatory cytokines and other immune cells, leading to immune suppression.

Impact of Immune Suppression on Stroke Outcome

Immune suppression following stroke can have significant impacts on the recovery and outcome of patients. It can increase the risk of infections and other complications, leading to longer hospital stays and increased mortality rates.

It can also impair the neurogenesis and synaptogenesis in the brain, leading to long-term disabilities such as cognitive impairments, speech difficulties, and motor deficits. Moreover, immune suppression can interfere with the efficacy of immune-based therapies that are currently being developed as a treatment for stroke.

Treatments for Immune Suppression following Stroke

The management of immune suppression following stroke is currently limited to supportive care and the prevention and treatment of infections. Antibiotics and antifungal agents are commonly used to prevent and treat infections.

Immune-based therapies such as interferons, cytokines, and stem cell therapies are still in the experimental stage and have shown promising results in preclinical studies. However, further research is needed to determine their safety and efficacy.

Prevention of Immune Suppression following Stroke

Preventing immune suppression following stroke is crucial in reducing the risk of complications and improving the patient’s outcome.

Prophylactic treatment with corticosteroids has been shown to reduce the risk of infections and improve the clinical outcome in some studies. However, the use of corticosteroids is controversial due to their immunosuppressive effects.

Other strategies that may prevent immune suppression include optimizing the management of blood pressure and glucose levels, improving the nutritional status, and promoting early mobilization and rehabilitation.

Conclusion

Immune suppression following stroke is a complex phenomenon that can have significant impacts on the recovery and outcome of patients.

The mechanisms that lead to immune suppression are not well understood, and there is currently no specific treatment available. The prevention of immune suppression through supportive care and optimizing the management of other comorbidities may reduce the risk of complications and improve the patient’s outcome.

Further research is needed to understand the mechanisms that underlie immune suppression and develop effective treatments to prevent and manage this condition.