How does our body's immune system distinguish between pathogenic microorganisms and commensal?

Submitted by blue_sloth999 t3_yqjkow in askscience

Microorganisms are an essential part of our body and even some of the pathogenic (potentially) microbes are also present on our body, classic example being Candida albicans. So how does our body allow such microbes to sustain in/on our body? And what makes our body to show an immunological response if such microbes are introduced externally? Do these have some different kind of proteins on their surface? How exactly is the distinction made?

14

Comments

You must log in or register to comment.

TaiCookie t1_ivp3xvi wrote

Your body doesn't. It's more microaganisms stay in their place, and don't travel to areas that can harm you. Bacteria on your skin is natural but is opportunistic ,if it enters a cut for example, it can cause infection. Even healthy gut bacteria are separated from your tissue via mucus layers.

5

askoemnzviwcasf t1_ivpbyev wrote

Yes and no, separation is an important part of keeping microbes out of areas where they can cause damage however the immune system regulates all microbes to some extent and recognizes them based on a variety of factors but some have a privileged status. This isn't really my area but commensal microbes engage in crosstalk with the immune system which is necessary for long term colonization.

Here's an article with more information: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4109969/

6

DumbDekuKid t1_ivs8ar2 wrote

Commensal microbes are established in gut at and after birth. There is always crosstalk between innate cells and gut microbiome. Homeostasis is established and immune priming (innate immune memory) occurs. If diet, disease, etc alter gut microbiome for a long duration, innate cells may lose healthy primed state. Here are three good places to start reading into details of various molecular mechanisms:

https://www.frontiersin.org/articles/10.3389/fimmu.2020.00282/full

https://www.tandfonline.com/doi/full/10.1080/19490976.2021.1939598

https://www.cell.com/immunity/pdfExtended/S1074-7613(22)00177-7

4

Rather_Dashing t1_ivtmymc wrote

Microorganisms actually within your body itself (not the GIT, lungs, skin etc) are always eliminated (well at least attempted to). On the other hand the immune system on the skin and mucous membranes are far more tolerant of microbes, a full immune response will not be triggered by the presence of microbes. Exactly how the immune system moderates the microbes at these sites is a pretty big topic.

3