Immunopharmacology, as its name suggests, is the branch of pharmacology that applies to the immune system. In general immunopharmacology describes the manipulation of the immune system and immune responses by pharmacological modulators, for the benefit of the host. This is an immense, and continually expanding field. Immunopharmacological therapeutics range from small molecule antihistamines, disease-modifying antirheumatics, and non-steroidal antiinflammatories to the more recently developed monoclonal antibodies and fusion proteins that can be used to treat autoimmune and chronic inflammatory diseases, as well as infection and cancer.
For a refresher on immunology and the immune system users can refer to sections on the Immunopaedia website, including The Basics of the Immune System, Advanced Immunology, and the Innate Immune System. Immunopaedia produces free online courses (free registration required), for example providing Core Immunology Modules, so you can test your own knowledge.