In 2025, we attended the 19th International Congress of Immunology, hosted by the International Union of Immunological Societies, in Vienna, Austria, and recorded daily episodes discussing highlights of the conference. Here is the third of five special episodes from the meeting. Brenda and Jason discuss sessions on CD4+ T cells in Hepatitis B infections and how amoebas make their way to the brain. They also cover research on the effects of antibiotics on immunotherapy, and what we can learn about allergies by comparing pet shop and lab mice.