The relation of our immune function to the microbial community of our gut is well established . However, the relation of our skin’s microbiome is a much newer topic, and a significant amount of research has recently been carried out to try to determine the intricate relationship that exists.
So how much does the skin’s microbiome influence our immunity and health?
Some of the more recent research suggests that the microbial communities of our skin play a significant role in several factors directly related to its immunity. And specific bacterial strains have been identified as a potentially sources of protection versus a myriad of pathogens .
This relation is best demonstrated by mice raised in completely sterile conditions, which results in the inability for the skin of these mice to properly defend against various pathogens, opportunistic bacteria and viruses .
How the Microbiome Modulates Skin Immunity
There is only a finite amount of space and nutrients available at the skin surface. Studies have shown, the presence of one bacteria will often result in a pronounced ability of the skin to defend against other competing pathogens. Thus, the more adapt bacteria will forcefully squeeze out it’s competitors.
Now let’s examine some of the most common ways that the microbial community of our skin affects it’s health and stability.
Production of Antimicrobial Compounds
A significant number of bacteria have been shown to produce antimicrobial compounds (peptides). These antimicrobial compounds are capable of successfully inhibiting or destroying similar and competing bacteria .
As a result, they may be able to directly enhance our skin’s immune function by assuming some of its work in the fight against various pathogens.
Increased Production of Antimicrobial Peptides
Another observed phenomenon is that the presence of some relatively weak bacteria is able to stimulate antimicrobial peptide production by the skin . This increased production of antimicrobial peptides, in essence, prepares the skin to defend itself against pathogenic infection.
Priming of Antimicrobial Compounds and Immune Function
Similar to the increased peptide production discussed above, some bacteria is capable of stimulating the overall immune functioning of the skin. This stimulated immunity (such as increased recruitment of mast cells) in-turn results in skin that is more prepared to defend itself against other, more dangerous bacteria.
Inhibition of Biofilm Formation of Other Bacteria
Biofilms offer protection for bacteria and increase their tolerance to antimicrobial agents . As bacteria compete, some are able to effectively inhibit the production of others by interfering with the biofim production process.
For example, a bacteria by the name of Staphylococcus epidermidis (a relatively nonthreatening bacteria) has been demonstrated to inhibit the formation of Staphylococcus aureus’s (a more problematic bacteria) biofilm .
Regulation of Cytokine Production and Potential to Decrease Inflammation
Cytokines are small proteins that are a major component of cellular communication. And specific bacteria have been shown to directly affect the regulation of inflammatory cytokines.
For example, it has been demonstrated that the presence of Staphylococcus epidermidis at specific skin sites leads to local regulation of cytokine production and decreased levels of inflammation .
Influence on T Cells
There is evidence that suggests that the presence of some bacteria is essential for proper T Cell functioning and overall immunity.
This has been demonstrated by germ-free mice who failed to produce an adequate immune response to Leishmania (parasite), even after recolonization of the gut by healthy microflora. Simple exposure of these mice to Staphylococcus epidermidis alone was enough to regulate T cell levels and restore the immune deficiency .
Viruses have been studied the least
Viruses, which are also found on the skin surface, have not yet been adequately studied. The few studies that did try to analyze this diverse aspect of the microbiome have concluded that their diversity likely plays a crucial role in the immunity and functioning of the skin. Perhaps in the future this area may uncover some pivotal findings, which may drastically change the overall view of the whole microbiome.
This section examined how the diversity and composition of the skin’s microbial community impacts it’s immune functioning. Key points include:
- The microbial communities of the skin appear to be a critical component of it’s immune strategy and lack of diversity has been associated with various skin issues
- Limited nutrient and space availability lead to microbial competition and this has a direct impact on the stability of the skin
- Certain microbes have been shown to produce antimicrobial peptides (vital component of protection), while others can stimulate their production
- The presence of a diverse microbial community helps constantly challenges the skin’s immune response and regulates the presence of defense cells
- Microbes often rely on biofilms for protection and it has been shown that certain microbes can inhibit their competitor’s biofilm production
- Microbes can influence cytokine production (major component of cellular communication) and modulate inflammation
- Some experiments in mice have shown a direct relationship between the presence of certain microbes and modulation of T Cell functioning