Immunopathology of Abortions-An Overview

Mewari NS and Chauhan RS (2020). Immunopathology of Abortions-An Overview. Journal of Immunology Immunopathology, 22(1): 92-127.

Expulsion of a dead foetus prior to the normal full gestation period is called abortion. Many fertilised ova, embryos or early feotuses may be aborted without being seen. This is especially true in beef cattle, sheep and other animals not closely observed. In the cow, abortions occurring before the fifth month of gestation are seldom followed by retention of the placenta, but those occurring after four months of gestation are frequently characterised by retention. Abortion is mostly due to infection of the foetus, placenta or the uterus as these conditions cause the death of the foetus. The nature of the causative agent of the abortion may determine the degree of damage to the foetal membranes and endometrium and the frequency of retained afterbirths and sterility that follows the abortion. The main diseases/causal agents associated with abortions in animals are brucellosis, vibriosis, trichomoniasis, listeriosis, epizootic bovine abortion, leptospirosis, abortion in mares by Salmonella abortus equi and equine herpes virus, equine viral abortion, equine Rhinopneumonitis virus (equine influenza), equine viral arteritis, bovine herpes virus-1 in cattle, Chlamydia psittaci, Mycobacterium tuberculosis, Toxoplasma gondii, Mycoplasma mycoides, abortion caused by the virus of Infectious Bovine Rhinotracheitis, mycotic abortion in cattle and sheep caused by Aspergillus sp., Coccidioides sp. and Absidia sp. and some toxins/poisons are also known to cause abortions. Immunopathology includes the disorders of the immune system characterised by increased response or hypersensitivity, response to self-antigens (autoimmunity) and decreased responses (immunodeficiency). Control of diseases requires a host inflammatory response, which is likely to contribute to pathology and abortion. Mouse models have been widely used to provide insight into the role of specific immune cells in controlling infection and disease. In this article, we will review current knowledge of the innate and adaptive immune responses required for resistance to various diseases associated with abortions and the events that lead to the development of immunopathology and the natural regulatory mechanisms that limit excessive inflammation during the infection.