In Chapter 18 of The Catcher in the Rye, Holden mentions his former teacher, Mr. Antolini:
Anyway, I gave old Jane a buzz again, but her phone didn't answer, so I had to hang up. Then I had to look through my address book to see who the hell might be available for the evening. The trouble was, though, my address book only has about three people in it. Jane, and this man, Mr. Antolini, that was my teacher at Elkton Hills, and my father's office number. I keep forgetting to put people's names in.
Later, in Chapter 22, Holden mentions him again to Phoebe:
Old Phoebe didn't say anything for a long time. Then, when she said something, I got up from the bed then, because what I wanted to do, I wanted to phone up this guy that was my English teacher at Elkton Hills, Mr. Antolini. He lived in New York now. He quit Elkton Hills. He took this job teaching English at N.Y.U.
And in Chapter 23, Holden tells the sordid backstory involving James Castle:
He was about the best teacher I ever had, Mr. Antolini. He was a pretty young guy, not much older than my brother D.B., and you could kid around with him without losing your respect for him. He was the one that finally picked up that boy that jumped out the window I told you about, James Castle. Old Mr. Antolini felt his pulse and all, and then he took off his coat and put it over James Castle and carried him all the way over to the infirmary. He didn't even give a damn if his coat got all bloody.
Mr. Antolini has a chance to rescue Holden, to be a Deus ex Machina ("God out of the machine": “a plot device or character that rescues a hopeless situation”). He had already rescued James Castle (initials "J. C." for "Jesus Christ," a martyr) from the rubbernecks. Now, Holden wants Antolini to be his catcher in the rye and rescue him from suicide or mental breakdown.
Mr. Antollini is very much like the voice of Salinger: Mr. counter-culture professional. His advice says that Holden is “in for a terrible fall”:
The mark of the immature man is that he wants to die nobly for a cause, while the mark of the mature man is that he wants to live humbly for one.
Salinger discredits Antolini in the end by casting him as possible gay pedophile (no rescuing; no morals). So, Salinger uses Antolini as a kind of "red herring," a false-savior in order to show the alienation of the modern teenager from the adult world.