Antibodies are naturally produced by plasma cells within the human body to mediate an adaptive immune response against invading pathogens. There are five predominant antibodies produced, each specialized to execute certain functions. Antibodies gain the ability to identify a diverse range of antigens by genetic recombination of different elements of its structure and while the affinity for a specific antigen derives from affinity maturation and somatic recombination processes. Antibodies have a plethora of clinical applications, the most important being their use in combating autoimmune conditions and cancer, conferring passive immunity, and their diagnostic applications.
Antibodies are produced primarily to mediate the immune response towards foreign pathogens, as part of the adaptive immune response. Pathogen recognition by B cells in secondary lymphoid organs allows differentiation into memory B cells and plasma cells. Memory cells remain to protect against subsequent attacks from the same pathogen while plasma cells produce antibodies specific for that pathogen. Vaccines rely on this concept, wherein a segment of the pathogen gets introduced to the individual such that an initial immune response is mounted and antibodies are more readily present when the real infection subsequently occurs. The five antibody classes produced by the body include IgG, IgM, IgA, IgD, and IgE. IgM is the first antibody produced and acts as a B-cell surface immunoglobulin(Ig). Complex signaling pathways then induce isotype switching to produce immunoglobulins more fit for fending off the particular pathogens.
Antibodies have been revolutionary in the field of medicine. They are often mandatory in an emergent response, such as in the case of Clostridium botulinum. Upon exposure, patients receive antibodies that confer immunity against the bacteria. Substantial harm can incur before the body naturally carries out an adaptive immune response; therefore, this intervention is essential; this is a form of passive immunity in which preformed Igs are given to the patient. In contrast, active immunity is one's body naturally producing antibodies in response to a pathogen, as seen in, for example, the seasonal influence virus. Patients with immunodeficient conditions such as Bruton agammaglobulinemia or selective IgA deficiency lack an innate ability to produce the entire set of antibodies required to maintain a healthy immune system. Again, the antibodies are passively introduced into the individual to sustain an immune system.
Below is the schematic diagram of the basic unit of immunoglobulin (antibody): 1. Fab 2. Fc 3. heavy chain (consist of VH, CH1, hinge, CH2 and CH3 regions: from N-term) 4. light chain (consist of VL and CL regions: from N-term) 5. antigen binding site 6.