Neuropathology of Immunosuppression

Abstract

Traditionally, the brain has been considered an "immunologically privileged" organ. Under normal conditions, the blood-brain barrier (BBB) is highly effective in preventing both cellular and humoral constituents of the blood from entering the brain parenchyma. In certain pathological conditions, such as viral infections and demyelinating disorders, the BBB may become altered, activated T cells and monocytes may gain access to the brain parenchyma, and microglia may assume the functions of antigen-presenting cells and macrophages. Naturally-occurring or clinically-induced immunosuppression may dramatically alter various cellular and/or humoral aspects of the immune system. Consequently, the brain may become susceptible to disorders that would otherwise be excluded or may develop more severe manifestations of diseases, such as certain infections. This review considers the neuropathologic aspects of various conditions that may be encountered in the setting of both acquired and inherited immunosuppression. The major categories include infectious, neoplastic, vascular, and metabolic disorders. The review also briefly addresses the neuropathology of complications of chemotherapeutic agents, radiotherapy, and organ transplantation inasmuch as they often occur in the clinical setting of acquired immunosuppression.

History of allergies and autoimmune diseases and risk of brain tumors in adults

“…Clinical evidence suggests that occurrence of certain infections and nervous system lymphoma and, possibly, glioma in immunocompromised patients might result from an impaired immune surveillance. [37][38][39] Recent experiments confirm that activated T cells can nonspecifically cross the blood-brain barrier and that populations of brain parenchymal cells can produce a wide range of cytokines and express class I and II major histocompatibility complex (MHC) molecules necessary for antigen presentation. 40,41 On the other hand, an effective antitumor response is lacking in most glioma patients and immunotherapies have not yet been shown to be consistently effective.…”

Inflammatory Responses and Regulation in Parkinson’s Disease

“…Under normal conditions, the central nervous system (CNS) and the brain especially are considered to be immune privileged (Neuwelt and Clark 1978;Smith, DeGirolami et al 1992;Lotan and Schwartz 1994). Any immune response is very highly regulated with a finely balanced anti-inflammatory environment within the CNS combined with vigilant immune surveillance by circulating immune cells and those that are resident in the CNS.…”

Etiology and Pathophysiology of Parkinson's Disease

“…Neuroinflammation is an important defense mechanism against pathogens and environmental toxins damaging the brain. Under normal conditions, the central nervous system (CNS) and the brain especially are considered to be immune privileged (Neuwelt and Clark 1978;Smith, DeGirolami et al 1992; Lotan and Schwartz 1994). Any immune response is very highly regulated with a finely balanced anti-inflammatory environment within the CNS combined with vigilant immune surveillance by circulating immune cells and those that are resident in the CNS.…”