mRNA and DNA: The Basics
mRNA is a complex molecule that contains the instructions, the "code", used by a cell to make a specific protein.
mRNA is itself made from DNA, but only when a new protein is needed.
DNA is a very, very complex molecule that contains the code for every protein that the body needs.
Every cell in the body has a DNA molecule, and it's the
same DNA molecule in every cell, regardless of cell type.
It's the same in a skin cell, as in a liver cell, as in a brain cell, as a pancreas cell etc.
When a cell needs to make a protein, say a skin cell needs to repair a cut,
it accesses that tiny part of its DNA molecule needed to make the skin protein,
and creates an mRNA molecule with the same specific code, by a process called Transcription.
(The cell then uses the mRNA to make the protein by a process called Translation.)
How does the skin cell know which tiny part of its DNA to select ?
No one knows !.
But there's a noble prize waiting for whoever figures it out.
However, it's vital that only
skin cells make skin proteins,
and that
skin cells don't make brain proteins,
brain cells don't make ovary proteins,
ovary cells don't make insulin etc.,
or the body would disintegrate in chaos.
mRNA Vaccines and Immunity.
An essential attribute of the immune system is its ability to distinguish what's a normal part of the human body,
called
"self", from what is "not-self"
(viruses, bacteria, fungi, pollens, etc) . . . so it can attack and eradicate only the not-self .
The immune system doesn't just produce antibodies;
it has many components which continuously interact with each other,
e.g. B-cells, T-cells, Killer cells, and a group of molecules called the Major Histocompatibility Complex (MHC).
All of the immune system components work closely together to eradicate the not-self,
and to destroy any self cells containing not-self,
e.g. lung cells infected with a virus !.
The MHC is the key to determining self from not-self,
although the MHC sometimes makes mistakes, resulting in diseases
such as Lupus, Multiple Sclerosis, Type 1 diabetes,
in which the immune system attacks self (these diseases are known as "autoimmune" diseases).
The precise nature of the components of a person's immune system,
is itself determined by that person's DNA, and so varies from person to person
. . . which likely explains why some people get Lupus or MS or Type 1 diabetes, but others don't.
mRNA Covid Vaccines
mRNA Covid vaccines take the form of a "Lipid Nanoparticle" (LNP), essentially an mRNA molecule inside a fat bubble.
The early hypotheses claimed that: