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PeerJ. 2016 Nov 17;4:e2705. eCollection 2016.

Ficolin-2 inhibitors are present in sera after prolonged storage at -80 °C.

Author information

1
Division of Pulmonary, Allergy, and Critical Care Medicine, University of Alabama at Birmingham , Birmingham , AL , United States.
2
Division of Gerontology, Geriatrics, and Palliative Care, University of Alabama at Birmingham, Birmingham, AL, United States; Comprehensive Center for Healthy Aging, University of Alabama at Birmingham, Birmingham, AL, United States.
3
Division of Gerontology, Geriatrics, and Palliative Care, University of Alabama at Birmingham, Birmingham, AL, United States; Birmingham/Atlanta Geriatric Research, Education, and Clinical Center, Birmingham Veteran's Affairs Medical Center, Birmingham, AL, United States.
4
Division of Pulmonary, Allergy, and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, AL, United States; Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, United States.

Abstract

Ficolins can activate the lectin pathway of the complement system that provides innate immune protection against pathogens, marks host cellular debris for clearance, and promotes inflammation. Baseline inflammation increases with aging in a phenomenon known as "inflammaging." Although IL-6 and C-reactive protein are known to increase with age, contributions of many complement factors, including ficolins, to inflammaging have been little studied. Ficolin-2 is abundant in human serum and can recognize many target structures; therefore, ficolin-2 has potential to contribute to inflammaging. We hypothesized that inflammaging would alter ficolin-2 levels among older adults and examined 360 archived sera collected from older individuals. We found that these sera had apparently reduced ficolin-2 levels and that 84.2% of archived sera exhibited ficolin-2 inhibitors, which suppressed apparent amounts of ficolin-2 detected by enzyme-linked immunosorbent assay. Fresh serum samples were obtained from donors whose archived sera showed inhibitors, but the fresh sera did not have ficolin-2 inhibitors. Ficolin-2 inhibitors were present in other long-stored sera from younger persons. Furthermore, noninhibiting samples and fresh sera from older adults had apparently normal amounts of ficolin-2. Thus, ficolin-2 inhibitors may arise as an artifact of long-term storage of serum at -80 °C.

KEYWORDS:

Complement; Ficolins; Lectin pathway; Lectins; Storage artifacts

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