This is incorrect with several unproven virology theories blended together. Immune systems are oriented to barriers between internal & external.. most of what is classified as viral illness is introduced at eyes, nose & mouth with T-cell response initially later B-cells may add backup defenses. Injecting mRNA is an old lab tool known as TRANSFECTION it's also how all virology is done with CRISPR sequences transfected into cell culture replicated by E.coli or other bacteria then stuffed into rodents to model disease & design vaccines.. it's also known as Gain of Function which is pure clones not a triumph of virology over nature. https://web.archive.org/web/20161206155142/http://www.gryphonscientific.com/wp-content/uploads/2016/04/Risk-and-Benefit-Analysis-of-Gain-of-Function-Research-Final-Report.pdf

Transfection of ANY and ALL non-self proteins triggers immune systems to destroy the non-self proteins and it made headlines in 1999 when promise of genetic modification to cure disease was shown to be total failure w Biotech Death of Jesse Gelsinger.. turns out even the most benevolent aim can't fool Mother Nature. Spike is irrelevant the body ALWAYS destroys non-self proteins.
https://web.archive.org/web/20080517050534/http://www.nytimes.com/library/magazine/home/19991128mag-stolberg.html