Our immune system - Miracle weapon against cancer? | DW Documentary

The immune system is essential for survival, protecting against infection, harmful substances, and cancer, but it can also pose a threat. It's a powerful and complex system, distributed throughout the body, with 70% of its cells in the intestines. Recent insights, partly due to COVID-19, have revealed its potential beyond microbe protection, especially in fighting cancer.

While some immune components are present at birth, much develops later. Natural birth exposes babies to beneficial microbes from the mother's vaginal and intestinal flora, unlike Cesarean births, which lead to colonization by oral and skin microbes. Breastfeeding, exposure to the environment, and avoiding excessive hygiene in early childhood are crucial for immune system development, as seen by the surge in children's hospital visits after COVID-19 lockdown measures were lifted.

The immune system has two main pillars: innate and acquired. The innate system, active from birth, reacts quickly to pathogens with cells like macrophages and natural killer cells, recognizing threats without prior training. If overwhelmed, the acquired immune system, with its targeted weapons and memory, takes over. This system, activated by vaccination, relies on T cells (trained in the thymus) and B cells (producing antibodies) to fight infections and remember past threats.

Newborns inherit antibodies from mothers, but these fade after 3-6 months. Lack of T cells leads to severe infections, prompting T-cell screening in newborns. B cells, which transform into plasma cells to release antibodies, are crucial for marking and destroying pathogens. Eliel, an 8-year-old with Bruton's disease, cannot produce B cells himself and requires lifelong antibody infusions.

COVID-19 was a novel virus, and initial immune responses were crucial. Age, pre-existing conditions, and compromised immune systems were major risk factors. Many COVID-19 deaths resulted from an excessive inflammatory response rather than direct viral damage. Research by Donna Farber at Columbia University showed children's immune systems possess more 'naïve' T cells, making them more effective at fighting new viruses like COVID-19 compared to adults, who have more memory T cells.

A study by Lluis Quintana-Murci at the Pasteur Institute identified five key factors influencing immune cells: genetics, age, sex, smoking, and cytomegalovirus (CMV) infection. CMV, a common herpes-family virus, permanently alters the immune system. The study also confirmed slight differences in male and female immune systems, with men more susceptible to infectious diseases and women to autoimmune conditions.

Most immune cells reside in tissues, lymphoid organs, and barrier sites like the lungs, intestines, and skin. These local immune militias are trained by the microbiome – the diverse community of bacteria, viruses, and fungi in and on our bodies. This microbial contact at birth is critical for immune system development, teaching it to distinguish between harmful and harmless bacteria. A diverse gut microbiome, with hundreds of bacterial types, is essential for healthy immune function.

The gut plays a central role in controlling the entire immune system. Doctors observe a decrease in microbial diversity in patients with inflammatory and abdominal issues. To foster a healthy microbiome and immune system, avoiding sugar and highly processed foods is recommended. A diet rich in vegetables, fiber, legumes, and fruits (especially berries for their healthy pigments) is beneficial, as are anti-inflammatory omega-3 fatty acids. Regular exercise, sufficient vitamin D, and adequate sleep also contribute to a strong immune system.

Karsten Krüger's research at Justus Liebig University investigates how exercise influences immune system aging. Immune aging is normal, but its speed depends on activity levels. His study found that individuals over 55 who exercised regularly and maintained a healthy diet had younger, more effective T cells, comparable to people 20 years younger. This demonstrates the power of lifestyle in preserving immune function.

Cardiologist Wolfram Poller's research at the Icahn School of Medicine has revealed the detrimental effects of stress on the immune system. Acute stress leads to a sharp increase in neutrophils (innate immune cells) and a drop in B and T lymphocytes (adaptive immune cells), which retreat into bone marrow. This weakens the immune response to viral infections, increasing their severity and mortality in animal models. Chronic stress negatively impacts the adaptive immune system, hindering its ability to fight infections and respond to vaccinations. Therefore, stress management is crucial for immune health.

Autoimmune diseases occur when the immune system mistakenly attacks the body's own cells, leading to conditions like psoriasis, rheumatoid arthritis, or type 1 diabetes. These diseases arise from a combination of genetic predisposition and environmental factors such as infections, pollutants, and the microbiome. Autoimmune diseases are on the rise, with approximately 80 known types, and statistically affect women more often than men. This may be linked to sex hormones or the presence of two X chromosomes in women, which carry immune-related genes.

Immunotherapy is a promising area of research, particularly for cancer treatment. Dirk Jäger at Germany's National Center for Tumor Diseases explains that our immune system typically prevents many tumors by recognizing and destroying cancer cells. In cases of cancer, the immune system needs a boost. Immunotherapy aims to strengthen the immune system's defense mechanisms, often focusing on T cells, to recognize, kill, and prevent relapse of tumor cells. Therapies include personalized cancer vaccinations and the multiplication of a patient's own T cells to fight malignant tumors.

Immunotherapy is becoming an integral part of cancer treatment, but research is still in its early stages. Scientists are also exploring how to suppress excessive immune responses in autoimmune diseases and allergies. The ultimate goal is to strengthen the body's defense mechanisms while maintaining balance. An immune system that is too weak cannot protect, but one that is too strong can cause harm.