Why is 'immune' used with 'to'?

A recent news item reported :

... they are also concerned about his argument in a 2009 legal article that a sitting president should be immune to prosecution.

The OED states that the adjective 'immune' has three primary meanings :

• free or clear (of or from)

• exempt from

• wholly protected from

but then the OED states another meaning :

• having immunity to

I do not understand how the concept of 'to' arises.

'Immune' is to be exempt from, clear of, clear from, untouched by, totally protected from .......

How does the concept of 'to' arise ?

EDIT: Following a (sadly deleted ?) answer which also noted the usage of 'against' I am adding a link to the Ngram for 'immune to/immune from/immune against'. There seems to have been a difference between AmE and BrE in the early 20th century but nowadays there is agreement by both that 'to' is more common and 'against' is very rare.

I then added 'immunity to/immunity from/immunity against' and saw something interesting :

The wording 'immunity from' prevailed in the 19th century and then, I suppose, the concept of vaccination changed the way that immunity was regarded. The graph shows the changes.

I note that your example is from BBC News, a British source, saying the source is a legal article but neither quoting that article nor giving its legal citation. That is one reason that I think "immune to prosecution" is not the most frequently used construction.

In my thirty-five years practicing law in the USA, I have read and heard only "immune from prosecution". It's as if there's a giant bulletproof window around the one "immune".

In the context of an American president being immune from prosecution, the doctrine of "sovereign immunity" is related. This is a a legal doctrine dating from European monarchs, "sovereigns". The president is not a sovereign, rather the nation is sovereign. Criminal prosecution and civil lawsuits against a sitting president would cripple his ability to work as the nation's chief executive. That is the policy reason for sovereign immunity.

"Immune to" may be more frequent in a medical context. I have also heard of parents who were "immune to" children's tantrums, in the sense of being able to ignore the tantrums.

As stated in one of the comments, prepositions can be flexible. Immune works with "to", "from", and "against", and all are used in the USA.

The usage of the prepositions to and/or from is still an open issue. The prepositions essentially introduce different concepts as suggested in the following article from Merriam-Webster.

The traditional advice given by usage commentators is that you become immune to a disease or a drug, but immune from something when the object is some kind of obligation or duty, such as taxation, or something that can happen to you, such as prosecution. (In Latin, immunis means "exempt from public service.")

Some commentators recommend determining the appropriate preposition based on the relationship between the affecting thing and the object being affected. As Bryan Garner explains in Modern American Usage, "What you’re immune from can’t touch you; what you’re immune to may touch you, but it has no effect."

So if you are immune from prosecution, the prosecutor cannot go after you; if you are immune to a suitor's charms, the suitor can keep wooing you, but it would be to no avail. A person immune from criticism cannot be criticized; a person immune to criticism can be criticized but doesn't let the criticism bother them.

Actual usage tends to be somewhat murkier, particularly when the affecting thing is expressed in abstract or figurative language:

• Williams said Kansas is not immune to earthquakes. There are fault lines near Manhattan, and the eastern half of the state sits between two major mid-continental faults… — William Klusener, _The Morning Sun _(Pittsburg, Kansas), 9 Nov. 2011

• Liberals are not immune from temptation and hubris even when they mouth correct sentiments. — National Review, 2 Sept. 2013

Since the very nature of the word implies a kind of separation or distancing—either from disease or trouble—it's understandable that from is sometimes preferred. Are there other options? Once in a while we run into the occasional immune against, but this is rare:

• Third, the fortunate ones of us who do recover develop antibodies that leave us immune against a recurrence of the disease for a long time — Jared Diamond, Guns, Germs, and Steel, 1997

Here are some examples of adjectives that take "to" and "from" prepositions:
BOTH TO AND FROM
immune to/from

TO:
resistant to (not from)
impervious to (not from)
impermeable to (not from)
resilient to (not from)
vulnerable to (not from)
susceptible to (not from)

FROM:
exempt(ed) from (not to)
protect(ed) from (not to)
shelter(ed) from (not to)
save(d) from (not to)
preserve(d) from(not to)
rescue(d) from(not to)
excuse(d) from(not to)
except(ed) from(not to)

I kind of do see a pattern between the two groups. The words on the top are adjectives, also with noun forms available. However the words on the bottom are all verbs, all have adjective forms made from their past participle. This isn't the case with the words in the top group.

I'm sure this isn't a great rule, it's just an observation of mine.

Also, as to why both "from" and "to" can be used with "immune", I looked up the word "immune" in the Middle English Dictionary, which supposedly includes word usage between 1100-1500, and I got this definition:

(a) Free; ~ fro, exempt from (payment of tithes);
(b) ~ of, free of (sin, deceit).
Link

So it looks like even going back over 500 years the word "immune" was used with both preposition "to" and "from". The dictionary gives something like "free or exempted from the payment of tithes". As a second definition it says the preposition following is "of", as in "free of sin, deceit".

I'm not sure whether this fits in with my observation that "from" is used with adjectives resulting from something done (verbs). But if you compare the two definitions, being free from paying tithes I would imagine is exempting you (doing something to you), whereas being free of sin I would imagine doesn't involve performing an action, but is simply a description of a person (adjective).