Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024312 (lymphopenia)
 4,859 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The immune system has evolved elaborate mechanisms to respond to diverse antigens while minimizing the risk for autoimmune reactivity. During lymphopenia, however, some mechanisms that normally serve to maintain host tolerance are temporarily suspended. Peripheral T cells proliferate in response to self-antigens in lymphopenic hosts, but proliferation toward these same antigens is prevented when T cell numbers are normal. This process, termed homeostatic peripheral expansion, augments peripheral T cell number and limits repertoire skewing during recovery from lymphopenia and also predisposes lymphopenic hosts to autoimmune disease. This paper reviews murine and human settings in which autoimmunity occurs in the context of lymphopenia. We propose a two-hit model, in which lymphopenia plus another insult is sufficient to induce autoimmune disease. Among the secondary insults that appear sufficient to induce autoimmunity during lymphopenia are overproduction of IL-21 as occurs in the NOD.SCID mouse, depletion of Tregs as demonstrated in murine colitis and gastritis models, and tissue inflammation as seen in HIV infected patients who develop immune reconstitution inflammatory syndrome (IRIS). Delineating critical cofactors which result in autoimmune disease during lymphopenia can provide insight into the pathophysiology of naturally occurring autoimmune diseases as well as generating testable hypothesis for inducing tumor-specific autoimmunity in lymphopenic hosts with cancer.
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PMID:Autoimmunity during lymphopenia: a two-hit model. 1676 27

Lymphopenia and restricted T cell repertoires in humans are often associated with severe eosinophilic disease and a T cell Th2 bias. To examine the pathogenesis of this phenomenon, C57BL/6 Rag2-/- mice received limited (3 x 10(4)) or large (2 x 10(6)) numbers of CD4 T cells. Three to 5 months after transfer, mice that had received 3 x 10(4) T cells, but not those that received 2 x 10(6), developed fulminant macrophage pneumonia with eosinophilia, Ym1 deposition, and methacholine-induced airway hyperresponsiveness, as well as eosinophilic gastritis; esophagitis and other organ damage occurred in some cases. Donor cells were enriched for IL-4, IL-5, and IL-13 producers. When 3 x 10(4) cells were transferred into CD3epsilon-/- hosts, the mice developed strikingly elevated serum IgE. Prior transfer of 3 x 10(5) CD25+ CD4 T cells into Rag2-/- recipients prevented disease upon subsequent transfer of CD25- CD4 T cells, whereas 3 x 10(4) regulatory T cells (Tregs) did not, despite the fact that there were equal total numbers of Tregs in the host at the time of transfer of CD25- CD4 T cells. Limited repertoire complexity of Tregs may lead to a failure to control induction of immunopathologic responses, and limitation in repertoire complexity of conventional cells may be responsible for the Th2 phenotype.
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PMID:Lymphopenic mice reconstituted with limited repertoire T cells develop severe, multiorgan, Th2-associated inflammatory disease. 1720 52

In humans, limited T-cell receptor repertoire and lymphopenia are associated with severe eosinophilic inflammatory disease. A model of lymphopenia and reduced T-cell repertoire was created; C57BL/6 Rag2-/- mice received limited (30,000) or large (2 million) numbers of CD4 T-cells. Three to five months post-transfer, mice that had received 30,000 T-cells, but not those that received 2 million, developed fulminant macrophage pneumonia with eosinophilia, Ym1 deposition. methacholine-induced airway hyperresponsiveness, eosinophilic gastritis and esophagitis. These mice had strikingly elevated serum IgE (in CD3epsilon-/- hosts) and donor-cells were enriched for IL-4, IL-5 and IL-13 producers. Th2 pathology and serum IgE were enhanced when transferred populations were depleted of CD25+ CD4 Tregs, but was more severe when the effector population was derived from limited as compared to the large effector population. Pretreatment of Rag2-/- mice with 300,000 CD25+ CD4 Tregs prior to effector cell transfer prevented disease while pretreatment with 30,000 did not, despite the fact that there were equal numbers of Tregs in the hosts at the time of transfer of effector cells. Limited repertoire complexity of Tregs may lead to a failure to control immunopathologic responses and limited repertoire complexity of conventional cells may be responsible for the Th2 phenotype.
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PMID:Repertoire-dependent immunopathology. 1788 7

Autoimmune diseases develop in selected normal mouse strains when thymectomy (Tx) is performed at 3 days of age (d3-Tx). Insufficient T cell regulation after Tx may result from a defect in regulatory T (Treg) cells or from an augmented effector T (Teff) cell number/pathogenicity. We have previously shown that Tx at 3 wk (wk3-Tx), the age of massive islet Ag release, accelerates diabetes onset. We now have determined diabetes incidence in d3-Tx nonobese diabetic mice and compared the frequency and function of their Teff and Treg cells with those of wk3-Tx mice. We found that d3-Tx had no effect on diabetes incidence, but induced gastritis. After day 3 and week 3 Tx, Treg cells were fully competent and their frequency increased. The number of diabetogenic T cells was greatly amplified after wk3-Tx and likely overcame Treg cell control, leading to an early tolerance breakdown. By contrast, in d3-Tx mice, activation concerned few cells and Teff cell amplification remained controlled. This suggests that Tx enhances autoimmunity when it coincides with the first encounter of autoreactive T cells with their cognate Ag. The relationship between Tx-induced lymphopenia, tissue remodeling, and autoimmunity is discussed.
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PMID:Autoimmunity during thymectomy-induced lymphopenia: role of thymus ablation and initial effector T cell activation timing in nonobese diabetic mice. 1980 16

An adult male chinchilla (Chinchilla lanigera) presented with severe lethargy and tachypnea; the physical examination was otherwise unremarkable. Due to the animal's clinical condition, it was submitted for necropsy but died immediately prior to euthanasia. Clinicopathologic findings included leukocytosis with a left-shift neutrophilia and lymphopenia, azotemia, hyperphosphatemia, hyperglycemia, hyperlipemia, electrolyte imbalance, cholestasis, and hepatocellular damage. Neutrophilic enteritis with gramnegative bacterial colonization, hepatic lipidosis, interstitial pneumonia, suppurative tubulonephritis, erosive gastritis, cerebral edema, and lymphoid depletion were present microscopically. Attaching and effacing, eae-positive, Escherichia coli characterized by the presence of the intimin virulence factor was isolated from both the kidney and spleen. The cause of death was attributed to acute E. coli septicemia and subsequent disseminated intravascular coagulation.
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PMID:Enteric infection and subsequent septicemia due to attaching and effacing Escherichia coli in a Chinchilla. 2432 26


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