Rheumatology is a branch of medicine devoted to the diagnosis and therapy of rheumatic diseases. Physicians who have undergone formal training in rheumatology are called rheumatologists. Rheumatologists deal mainly with immune-mediated disorders of the musculoskeletal system, soft tissues, autoimmune diseases, vasculitides, and inherited connective tissue disorders. Many of these diseases are now known to be disorders of the immune system. Rheumatology is considered to be the study and practice of medical immunology. Beginning in the 2000s, the incorporation of drugs called the biologics (which include inhibitors of TNF-alpha, certain interleukins, and the JAK-STAT signaling pathway) into standards of care is one of the paramount developments in modern rheumatology. The impact factor of an academic journal is a scientometric index that reflects the yearly average number of citations that articles published in the last two years in a given journal received. It is frequently used as a proxy for the relative importance of a journal within its field; journals with higher impact factors are often deemed to be more important than those with lower ones.