there has been some really incredible progress in immunology recently. my partner deals with some immune system issues and the new therapies have made an incredible change in her quality of life, though there's still a long way to go.
i am a mere programmer so my understanding is limited but i was really impressed with Immune by Philipp Dettmer[1] of Kurzgesagt on youtube. it helped immensely with getting my bearings and being able to understand a good chunk of the systems involved at a high level. i tried my partners undergrad immunology textbook afterwards and it was overwhelming, so Immune is a great balance.