If you look at the right hand side of this picture. You see the "incidence of immune disorders" starts to increase dramatically around 1950. The first widely used antibiotics came out in the late 1940's. I don't think that's a coincidence.
There are other things that happened in the 1950s that could also help explain the rise of autoimmune diseases:
Poliovirus vaccine was introduced in the late 1950s, and it is speculated that because this eradicated poliovirus infection in Western countries, that allowed coxsackievirus B infections to become more fierce (because natural infection with poliovirus early in life may offer some immunological cross protection against other enteroviruses such as coxsackievirus B and echovirus).
In particular, the poliovirus vaccine is speculated to be responsible for the rise in type 1 diabetes, which is linked to coxsackievirus B1 and B4. And it's possible the poliovirus vaccine might have caused the massive rise in ME/CFS incidence that apparently occurred in the 1980s. ME/CFS is linked to coxsackievirus B and echovirus.
See this thread:
Did the introduction of the polio vaccine cause the massive rise in ME/CFS incidence in the 1980s?
So this underlines the urgent need to introduce a coxsackievirus B vaccine.
And pesticide usage increased dramatically in the Western world from the 1960s onwards (the graph on
this webpage). Pesticide exposure has been linked to various autoimmune diseases. So that could also help explain the rise in autoimmunity.
Also, if we assume that bacteria and antibiotics do play some role in the increased prevalence of autoimmune disease, it may be the bacterial infections themselves rather than the antibiotics used to treat them that are the culprits. Prior to antibiotics, a lot more people with bacterial infections would have just died of the infection, and therefore even if the bacterium they caught were to trigger autoimmunity, no one would know, because the person may not have survived the infection.
25% of OCD cases are thought to be due to an autoimmune condition triggered by Streptococcus bacteria, via molecular mimicry So that's one example of how bacteria might be triggering autoimmunity.
I came across
this article explaining a theory that the aminoglycoside class of antibiotics might play a role in triggering autoimmune disease due to the way they alter gene expression in human cells. Apparently aminoglycosides will cause human cells to read through stop codons in the human genetic code, producing a longer protein product, which it is speculated may then help trigger autoimmunity.