Understanding Immunopathology in Infectious Diseases

Immunopathology in infectious diseases is all about how our body's defense system, or immune response, interacts with germs. Sometimes, this interaction can cause harm to our tissues and lead to too much inflammation. Let's break down the main ways this happens:

1. Cytokine Storms:

   • During infections, our body can produce too many pro-inflammatory molecules called cytokines. These molecules help fight infections but can also set off too much inflammation. For example, in severe cases of the flu, a cytokine called IL-6 can spike really high, causing damage to the lungs and making the whole body inflamed.

2. T Cell-Mediated Immunity:

   • T cells help protect us from infections. However, when they get too activated, they might hurt our own body tissues. In viral infections like COVID-19, certain T cells can kill both infected and healthy cells, which leads to lung damage. This is especially true in bad cases of COVID-19 where the levels of these T cells are very high.

3. Antibody-Dependent Enhancement (ADE):

   • Sometimes, antibodies—our body’s defense proteins—can actually make infections worse. This happens when they help germs enter cells more easily instead of fighting them. This was seen in dengue virus infections, where antibodies from past infections led to severe sickness in some patients.

4. Immune Complex Formation:

   • When our body fights off germs, it can create clusters of antibodies and germs called immune complexes. These can settle in different tissues and cause inflammation and damage. For instance, about 10% of kids with a certain kidney issue, called post-streptococcal glomerulonephritis, have problems because of these immune complexes.

5. Molecular Mimicry:

   • Some germs have parts that look a lot like our own body tissues. This can trick our immune system into attacking our own tissues, leading to autoimmune diseases. A well-known case is rheumatic fever after strep throat, where the body’s response can accidentally harm the heart in about 3% of untreated individuals.

6. Chronic Inflammation:

   • If infections stick around for a long time, they can cause ongoing inflammation, which keeps damaging tissues. In tuberculosis, for example, the body forms lumps called granulomas that can lead to serious lung damage in about 20% of patients.

These points show how important it is for our immune system to work well. It needs to fight off infections but also avoid hurting our own body. The balance can be tricky, and when things go wrong, it can complicate the healing process.