Immunology is the branch of biomedicine that is concerned with the structure and function of the immune system. Subtopics include innate and acquired immunity, histocompatibility, the various cells of the immune system and the interaction of antigens with specific antibodies.
There has been exponential growth in the development, refinement and implementation of various laboratory techniques in immunology research. Early methods used tehcniques such as viral plaque assays, but more recent and advanced techniques include ELISA and ELISPOT assays. This is a meaty subject matter though, better suited for a more thorough discussion at a later date.