Immunopathological Disorders of Joints

The immune system in the body has also evolved with the development of the microorganisms to shield us from their harmful effects. The immune system protects not only from infectious organisms, but also from poisonous and allergic substances. There is a complex network of different organs, cells, proteins, humoral and cellular factors functioning in cascade to maintain the normal homeostasis in the body. The immune system has three main pillars, including anatomical and physical barriers, innate and acquired immunity. In conjunction with each other, these three elements of the immune system provide protection against any harmful agents. Immunopathological disorder happens when one of these mechanisms fails. This means that the defensive immune responses can also cause tissue damage. Accordingly, the study of diseases caused by the immune system is known as immunopathology and the diseases are known as immunopathological disorders. Such conditions are mainly described by excessive immune responses i.e., hypersensitivity, response to self-antigen i.e., autoimmunity, and inadequate immune response i.e., immunodeficiency. In joints, these immunopathological changes lead to the alteration in normal cartilaginous structure, joint capsule, and synovial membrane. However, the etiology of most of these conditions remains unknown, but it is suspected that both genetic and environmental factors play a pivotal role in the development of synovial inflammation as in diseases like rheumatoid arthritis, spondyloarthritis and osteoarthritis. Rheumatoid arthritis (RA) is an etiologically unknown, chronic inflammatory autoimmune disease. It is characterized by rheumatoid factor and peptide antibodies that are anticitrullinated. Various bacterial, viral, protozoal and fungal agents are involved in the infectious arthritis of domestic animals.