Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
The MBL pathway test evaluates how well the lectin arm of your complement system is working. Mannose‑binding lectin is a protein that recognizes certain sugar patterns on bacteria, viruses, and fungi, then triggers a cascade of complement proteins that help clear these microbes. This test is a functional assay that measures the ability of the lectin pathway to activate complement in the laboratory.
Results are typically reported relative to a healthy reference sample. The test is often performed alongside classical and alternative pathway assays to give a fuller picture of complement function.
Your complement system is a key part of innate immunity. If the lectin pathway is not working well, you may be more prone to some infections, especially of the respiratory tract, or have slower recovery from illness. Low activity can occur with inherited variations that reduce mannose‑binding lectin levels or affect associated enzymes, and it can also occur when complement proteins are being used up during active inflammation or certain illnesses.
Clinicians use this test when evaluating frequent or unusual infections, suspected immune deficiency, or conditions that may consume complement. It can also help pinpoint where a complement problem lies when combined with other pathway tests, guiding follow‑up and treatment decisions.
If your activity is within the expected range, your lectin pathway is likely functioning adequately. A reduced result suggests either a hereditary reduction in mannose‑binding lectin or related proteins, or an acquired issue such as increased consumption during illness. Some people with low mannose‑binding lectin never develop significant infections, so results are interpreted together with your health history and symptoms.
If results are low, your clinician may repeat testing when you are well, and may order related tests such as mannose‑binding lectin concentration, genetic studies, or other complement pathway assays. Management focuses on your overall risk, any current infections, vaccination status, and preventing complications, rather than the laboratory value alone.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Complement proteins are sensitive to delays, temperature, and repeated freeze‑thaw cycles. Hemolysis or using the wrong tube type can activate or inhibit complement in the sample and distort activity results.
Active infections, autoimmune flares, and recent surgery can consume complement or alter acute phase proteins, temporarily lowering or changing lectin pathway activity. Retesting after recovery may be recommended.
Complement inhibitors, certain monoclonal antibodies, immunosuppressants, and high‑dose corticosteroids can change complement activation or consumption. Recent plasma or antibody infusions may transiently normalize or alter results.
Most complement proteins are made in the liver. Liver disease or severe malnutrition can reduce production and lead to lower measured activity independent of genetic deficiency.
Young infants may have lower complement activity, and pregnancy or estrogen therapy can shift complement protein levels. These physiologic changes can influence interpretation.
EDTA and other chelating anticoagulants can block complement activation in vitro. Functional assays usually require properly processed serum; using the wrong tube may lead to falsely low activity.
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