The adaptive immune system is the “big gun”, later evolved, big brother of the innate immune system. The innate immune system acts a little like prejudice does in society. There is INSTANT RECOGNITION of a salient characteristic of many common disease-producing organisms, that are not present in the person being infected.
For instance, ENDOTOXIN is a lipopolysaccharide present in many bacteria, and is immediately recognized by Toll-like Receptors (TLR-4) on dendritic cells and macrophages. This triggers the Natural Killer (NK) cells to destroy the invader. The problem is that the innate immune system is indiscriminate, reacting against whole classes of molecules like a shotgun, and may produce unwanted damage. It also fails to recognize many genuine threats.
The ADAPTIVE immune system is more complex, discriminant, and SPECIFIC, but is SLOWER to gear up, and takes several days to be effective. Once engaged, however, it has a MEMORY for the infection that is SPECIFIC to the organism involved. This memory makes a SECOND EXPOSURE response much more rapid and comprehensive, AMPLIFIED as it is BY ANTIBODIES.
This first experience can be PROPHYLACTICALLY accomplished by VACCINES, so that the second, real exposure generates a RAPID PROTECTIVE RESPONSE. ATTENUATED vaccines are weakened, but LIVING ORGANISMS, and usually provide a more DURABLE immunity, but because they are living, they are more worrisome.
SPLIT-PRODUCT Vaccines are safer, but expose the immune system to a narrower range of pathogen markers, and may therefore be less Protective.. The FDA is very dedicated to SAFETY. Like all Bureaucracies, it is relatively independent of Political pressure, of which I am increasingly appreciative.
When the COVID-19 VACCINE, for example, is released to the general public, it WILL BE SAFE. The vaccine-deniers are mis-informed people who should not, in my opinion, be allowed to interfere with the HERD IMMUNITY that comes with having a supermajority of the population vaccinated.
— Dr. C.