The kidneys are one of the main excretory organs of the body. They filter waste products and regulate salt and water balance through nephrons; the basic functional unit.
In attempting to understand the many ways in which benign disease processes occur in the kidney, one must first review the normal structure and function of these vital organs.
Immune mechanisms are responsible for many benign diseases in the kidneys. Injury occurs via Type III hypersensitivity immune reactions in which the deposition of immune complexes triggers the activation of the complement cascade and elicits an inflammatory response.
Immune-complex formation occurs in response to exogenous (material from outside the body e.g. bacteria) or endogenous (elements from within the body e.g. nuclear proteins) antigens. This process of antigen-antibody binding may occur within the circulation or in the kidney itself (in-situ).
When immune-complex formation occurs in the circulation, the kidney is considered to be an “innocent by-stander”. Immune-complexes are filtered and become trapped as blood passes through the kidney.
Likewise, circulating antigens may also be filtered and deposited, thereby being “planted” in the kidney. In other cases, structural elements of the kidney, especially parts of the glomerulus, can become “foreign” or antigenic and are therefore known as “intrinsic” antigens. Subsequent binding of antibodies to either “intrinsic” or “planted” antigens will result in immune-complex formation.
The glomerulus is the part of the nephron responsible for filtering blood, as such, it is the primary site involved by immune-complex mediated diseases. Whenever immune-complexes are deposited or formed, the Type III hypersensitivty reaction is triggered, causing tissue damage and disease. Many of these diseases are therefore termed “glomerulonephritis” referring to the inflammatory nature of the injury.
Having reviewed the textbook Robbins and Cotran Pathologic Basis of Disease, 7th -9th editions:
1. List four (4) diseases you think illustrate this type of injury. For each disease, state:
a) Whether the antigen is exogenous, endogenous, intrinsic or planted
b) Whether immune-complex formation occurs in circulation or in-situ
Pathogenesis of Glomerular Diseases 