Immunodeficiencies in first defenses & Immunodeficiencies of the complement system

How do defects in epithelial barriers, pathogen recognition receptors, or peptides affect the immune response?

Defects in these first-line defenses can lead to increased susceptibility to infections. For example, the lack of defensins (small pore-forming peptides that kill bacteria) leads to increased opportunistic bacterial infections.

How can imbalances in normal microbiota contribute to immunodeficiencies?

Imbalances in normal microbiota can lead to competition for nutrients and space, disrupting the body's defense against pathogens.

What can defects in the complement system lead to?

Defects in any complement component can impair the immune system's ability to respond to microbes, increasing susceptibility to infections.

How do mutations in components involved in C3 activation affect immune function?

Mutations that impair C3 convertase formation or deplete C3 due to inhibitory protein mutations result in an impaired ability to fix C3, leading to susceptibility to microbial infections.

What happens when there are mutations in the C5-C9 genes?

Mutations in C5-C9 genes impair the generation of the membrane attack complex (MAC), resulting in increased susceptibility to certain bacterial infections.