Immunity system complexity: innate and secondary (Introduction)

by David Turell , Thursday, January 19, 2023, 22:15 (456 days ago) @ David Turell

As shown in BCG research:

https://www.scientificamerican.com/article/an-old-tb-vaccine-might-help-stave-off-diabe...

"Mihai Netea, an immunologist and infectious disease clinician...says that BCG hasn’t helped reduce the number of COVID infections, but the evidence suggests that it could reduce disease severity. In a meta-analysis that he, Stabell Benn and Aaby published in Lancet Infectious Diseases on the effects of live vaccines against COVID, they found that across five trials, there was a 40 percent reduction in overall mortality in those who received BCG, compared with those who did not.

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"Broadly speaking, the immune system has two branches: the innate immune system, which provides a first response against infection, and the adaptive immune system, which takes longer to activate and is aimed at specific targets, or antigens. Vaccines typically work by activating the adaptive immune system’s T and B cells and triggering, in the latter, the production of antibodies to a specific antigen such as the spike protein of the coronavirus that causes COVID.

"Previously, researchers thought that the generalized response of the innate immune system was optimized for a rapid defense against infection and kept no persistent memory of an invading pathogen. But what Netea and others have shown over the past decade is that the innate immune system is capable of remembering previous encounters and if this system has prior exposure to the BCG vaccines, the next meeting with an invasive pathogen will trigger an enhanced response, such as the production of more signaling molecules called cytokines that attack microbial invaders.

"Netea and his colleagues have worked over the past decade to understand this phenomenon, which they call “trained immunity.” They have shown that BCG vaccination causes metabolic changes in immune cells such as monocytes and macrophages, which in turn alter either the placement or removal of chemical, or “epigenetic,” marks on DNA through processes known as methylation and acetylation. These marks serve as bookmarks for immune-related genes in the innate immune system and enhance the monocytes’ production of cytokines when challenged with an infection. “What BCG is doing is putting an epigenetic bookmark in your DNA. So when you need to read it, you already have the bookmark, and the book opens automatically at the right page,” Netea says.

"The researchers found that the BCG vaccine does not only affect the epigenetic marks in circulating innate immune cells such as relatively short-lived macrophages, which provide protection by consuming viruses or other invaders. It also alters marks on the DNA in stem cells in the bone marrow that produce new immune cells, which could explain how the effect of the vaccine can persist for many years."

Comment: it appears the innate immune system can also build up a library of responses. This is all automatic. All antibodies ae made by adding the same killer proteins to the foreign antigen.