Pneumonia, Acute Respiratory Distress Syndrome, and Early Immune-Modulator Therapy

Abstract

Acute respiratory distress syndrome (ARDS) is caused by infectious insults, such as pneumonia from various pathogens or related to other noninfectious events. Clinical and histopathologic characteristics are similar across severely affected patients, suggesting that a common mode of immune reaction may be involved in the immunopathogenesis of ARDS. There may be etiologic substances that have an affinity for respiratory cells and induce lung cell injury in cases of ARDS. These substances originate not only from pathogens, but also from injured host cells. At the molecular level, these substances have various sizes and biochemical characteristics, classifying them as protein substances and non-protein substances. Immune cells and immune proteins may recognize and act on these substances, including pathogenic proteins and peptides, depending upon the size and biochemical properties of the substances (this theory is known as the protein-homeostasis-system hypothesis). The severity or chronicity of ARDS depends on the amount of etiologic substances with corresponding immune reactions, the duration of the appearance of specific immune cells, or the repertoire of specific immune cells that control the substances. Therefore, treatment with early systemic immune modulators (corticosteroids and/or intravenous immunoglobulin) as soon as possible may reduce aberrant immune responses in the potential stage of ARDS.

Medical Conditions

“…Various pathogens cause pneumonia, and occasionally pneumonia can progress to ARDS, multiple organ failure, and death. The pathogens causing pneumonia may be the cause of ARDS, and the immunopathogenesis of ARDS may be the same as that of pneumonia [10]. Although risk factors such as being an infant, being elderly, comorbidity with other diseases, and immunodeficient states are associated with the development of ARDS in various respiratory infections, including influenza virus infection, previously healthy patients can also develop ARDS.…”

Additional corticosteroids or alternative antibiotics for the treatment of macrolide-resistant Mycoplasma pneumoniae pneumonia

“…Quinolones and tetracycline are not recommended in pediatric patients because of potential side effects such as arthropathy or tooth discoloration, and the use of these alternative antibiotics is not approved by the Korean Food and Drug Administration at present time10). During advanced MP pneumonia, host cell-derived substances from injured lung tissue may induce more inflammation, affecting the corresponding immune cells and prolonging morbidity; thus, early control of disease progression is important11).…”

“…Although antibiotics for bacterial pathogens and antivirals for viral pathogens can contribute to early recovery from the disease, some pneumonia patients experience a severe clinical outcome and even death, despite extensive antimicrobial treatment. This finding suggests that the immune status of a patient is an important factor in deciding the prognosis of the disease11). The precise mechanisms of lung cell injury in pneumonia resulting from various pathogens, including MP pneumonia, remain unknown.…”

“…The precise mechanisms of lung cell injury in pneumonia resulting from various pathogens, including MP pneumonia, remain unknown. Whole MP (or respiratory viruses) induce direct injury to target cells is unlikely because MP is probably an extracellular mucosal pathogen, and few intact MPs are found in pulmonary and extrapulmonary lesions, such as Stevens- Jonson syndrome or meningoencephalitis1112). Structural components of MP, such as lipoproteins from the cell membrane or secretary toxins such as community-acquired respiratory distress syndrome (CARDS) toxin, can induce inflammation and cytokine production1314).…”

“…The substances that induce lung inflammation either originate from the pathogens or from injured host cells and activated immune cells15). The hyper-immune reaction of the corresponding immune cells may be involved in target cell injury in the early stages of the disease, and early control of this type of immune disturbance may be crucial for prevention of pneumonia progression11). We have reported that systemic immune-modulators halt the progression of pneumonia, and induce rapid clinical and radiological improvement in patients with severe MP pneumonia or severe influenza pneumonia4816171819).…”