The Four-Way Stop Sign: Viruses, 12-Lipoxygenase, Islets, and Natural Killer Cells in Type 1 Diabetes Progression

Natural killer (NK) cells represent an important effector arm against viral infection, and mounting evidence suggests that viral infection plays a role in the development of type 1 diabetes (T1D) in at least a portion of patients. NK cells recognize their target cells through a delicate balance of inhibitory and stimulatory receptors on their surface. If unbalanced, NK cells have great potential to wreak havoc in the pancreas due to the beta cell expression of the as-yet-defined NKp46 ligand through interactions with the activating NKp46 receptor found on the surface of most NK cells. Blocking interactions between NKp46 and its ligand protects mice from STZ-induced diabetes, but differential expression non-diabetic and diabetic donor samples have not been tested. Additional studies have shown that peripheral blood NK cells from human T1D patients have altered phenotypes that reduce the lytic and functional ability of the NK cells. Investigations of humanT1D pancreas tissues have indicated that the presence of NK cells may be beneficial despite their infrequent detection. In non-obese diabetic (NOD) mice, we have noted that NK cells express high levels of the proinflammatory mediator 12/15-lipoxygenase (12/15-LO), and decreased levels of stimulatory receptors. Conversely, NK cells of 12/15-LO deficient NOD mice, which are protected from diabetes development, express significantly higher levels of stimulatory receptors. Furthermore, the human NK92 cell line expresses the ALOX12 protein [human 12-lipoxygenase (12-LO), related to mouse 12/15-LO] via Western blotting. Human 12-LO is upregulated in the pancreas of both T1D and T2D human donors with insulin-containing islets, showing a link between 12-LO expression and diabetes progression. Therefore, our hypothesis is that NK cells in those susceptible to developing T1D are unable to function properly during viral infections of pancreatic beta cells due to increased 12-LO expression and activation, which contributes to increased interferon-gamma production and an imbalance in activating and inhibitory NK cell receptors, and may contribute to downstream autoimmune T cell responses. The work presented here outlines evidence from our lab, as well as published literature, supporting our hypothesis, including novel data.

A case of myocarditis following neonatal meningitis caused by coxsackievirus B1 in spite of intravenous immunoglobulin treatment

Enteroviral infection is one of the most common neonatal infections, and most patients recover without complications. This report describes a neonate who experienced meningitis followed by myocarditis. A 4-day-old boy was admitted with fever, diagnosed with enteroviral meningitis and treated with intravenous immunoglobulin (IVIG). However, myocarditis was subsequently diagnosed in spite of IVIG treatment, and coxsackievirus B1 (CXB1) was revealed as a cause. A left ventricular aneurysm persisted even though the patient recovered with repeated high-dose IVIG treatment and cardiac supportive care. This report describes a rare case where myocarditis developed several days after a diagnosis of CXB1 meningitis in spite of IVIG treatment. It is important to pay attention to the patient's clinical condition until the end of the second viremia of enterovirus and to consider high-dose IVIG treatment when treating enteroviral infections for neonates.

High-degree atrioventricular block in a child with acute myocarditis

BACKGROUND

Viral myocarditis is a common cause of transient electrocardiogram (EKG) abnormalities in children. The clinical presentation of acute myocarditis ranges from asymptomatic infection to fulminant heart failure and sudden death. Many children present with nonspecific symptoms such as dyspnea or vomiting, frequently leading to misdiagnosis. EKG abnormalities are a sensitive indicator of acute myocarditis and are present in more than 90% of cases.

CASE REPORT

A 13-year-old female suffered a syncopal episode and was found to have high-grade atrioventricular (AV) block caused by acute presumed viral myocarditis. With close monitoring, the EKG abnormalities resolved over the following 48 hours. In this case report, we discuss the incidence, pathogenesis, and outcomes of conduction disturbances in acute myocarditis.

CONCLUSION

High-degree AV block can occur in patients with acute myocarditis, and higher-degree AV block is correlated with greater myocardial injury. Additionally, severity of pathological changes may reflect the reversibility of AV block. In the majority of cases, however, this rhythm disturbance is transient and does not require permanent pacemaker placement.