4 ms·
How does the immune system distinguish between native tissue and foreign tissue?
by biot 8y ago
How does the immune system distinguish between native tissue and foreign tissue?
- vibrio 8y agoMany ways you could a semester of immunology on this. High a level there are molecules called MHC (Major Histocompatability Complex), or HLA (Human Leukocyte Antigen). They are very important to the immune system in a number of ways. Any individual has a few sets of these, and there are many different genetic types of these molecules so the differences between any two people can be many. The immune system is even sensitive to their absence, since their down regulation is a strategy for some pathogens such as virus. Anyway, as the name MHC suggests, this is one way that the immune system detects foreign tissue.
- weberc2 8y agoApologies for an unsubstantial comment, but biology blows my mind. Do we know when these features in our immune system evolved? I assume something this foundational is shared with fish or maybe earlier?
- reubenswartz 8y agoVertebrates have an adaptive immune system. It’s astounding from a biological and information theory perspective. Genes basically mutate themselves so they can form an enormous variety of proteins instead of the typical one to one mapping of gene to protein. Then there is a protein selection process that weeds out those antigens that bind to the host of that don’t bind to anything, leaving those that can bind to foreign proteins. (There’s another process to replicate antigens when they attack something.) At least, that’s my primitive understanding. Come on HN, please someone fill in the real story, because I’d love to understand it better. :)
- vibrio 8y agoI think you described it pretty well. my version of the same: During their development Lymphocytes have 'gene cassettes' that get shuffled randomly so that the specificity of the receptor (antibody for cells, T cell receptor for T cells) is random for each individual lymphocyte cell during development. The ones that bind "Self" stuff are killed off during their development and the rest of them other just hang out waiting for something that binds their receptor. (There is a step here where T cells must bind to MHC within an affinity window to survive) If they find it the reproduce rapidly making many more cells with that specify. once amazing thing is that during that cell replication at the sites of antibody specificity the DNA copying gets sloppy, allowing new mutations to 'fine tune' the specificity of the antibody to the antigen (called somatic hypermutation). The cells that bind the tightest to the foreign antigen, reproduce the most robustly providing an 'evolution' of increasing affinity to the antigen. This stuff is only the tip of the iceberg - immunology it is amazing.
- odiroot 8y agoRead "The Red Queen" by Matt Ridley. You'd understand that and some more.
- TheForumTroll 8y agoLook for "Palestinian" in the passport.
- kmm 8y agoThere are enzymes in cells called proteasomes that degrade intracellular proteins that are damaged, not needed anymore or just old and ready to be replaced. The rest products are peptides, short chains of amino acids, some of which become bound to molecule called the Major Histocompatibility Complex 1, which is then transported to and presented on the surface of the cell. It functions more or less as an ID badge of the cell. Foreign cells, cancerous cells or cells infested by bacteria or viruses will present unknown proteins, which will trigger an immune response. An obvious solution would be to deactivate the MHC 1 in transplanted foreign tissue, but sadly that wouldn't work because the Natural killer cells in our immune system destroy cells without MHC 1. This is probably an adaption that evolved as bacteria evolved the capability to downregulate MHC 1 molecules to evade detection by other parts of the immune system.