Surfactant Protein A ELISA Assay
The Surfactant Protein A ELISA Assay is For Research Use Only
Size: 12×8 wells
Standard Range: 2-32ng/ml
Incubation Time: 70 minutes
Sample Type: Serum, cell culture supernatant and plasma
Sample Size: 40 ul
Alternative Name: SPA, SP-A
Surfactant protein A (SP-A), the most abundant apoprotein of pulmonary surfactant, is a hydrophilic hybrid molecule that belongs to the Ca2+-dependent animal lectin superfamily termed collectins. SP-A has multiple functions including participating in tubular myelin formation, regulating the recycling of surfactant lipids, and acting synergistically with the two lipophilic surfactant apoproteins to lower surface tension. In addition, SP-A plays a major role in host defense of the lung: it is an essential component of innate immunity and helps to activate acquired immunity. SP-A can act either as a proinflammatory or anti-inflammatory agent, increasing or decreasing production of inflammatory cytokines by inflammatory cells to either enhance pathogen killing or suppress inflammation under basal conditions. Finally, it has been shown that SP-A levels are altered during a number of disease states including adult respiratory distress syndrome (ARDS) and cystic fibrosis. Concomitantly, exposure of SP-A to severe inflammation may cause oxidation or nitration of the protein and result in inactivation. Inactivation of SP-A during disease states may therefore cause increased susceptibility to secondary lung infections.
Sample Preparation and Storage:
Specimens should be clear and non-hemolyzed. Samples should be run at a number of dilutions to ensure accurate quantitation.
- Extract as soon as possible after specimen collection as per relevant procedure. The samples should be tested as soon as possible after the extraction. Alternately the extracted samples can be kept in -20°C. Avoid repeated freeze-thaw cycles.
- Serum- Coagulate at room temperature for 10-20 minutes; centrifuge for 20-min at 2000-3000 rpm. Remove the supernatant. If precipitation appears, recentrifuge.
- Plasma- Use EDTA or citrate plasma as an anticoagulant, mix for 10-20 minutes; centrifuge for 15-min at 2000-3000 rpm. Remove the supernatant carefully. If precipitation appears, recentrifuge.
- Urine- Collect urine in a sterile container, centrifuge for 20-min at 2000-3000 rpm. Remove the supernatant. If precipitation appears, recentrifuge.
- Cell Culture Supernatant- Collect sample in a sterile container. Centrifuge for 20-mins at 2000-3000 rpm. Remove the supernatant carefully. When examining the components within the cell, dilute cell suspension with PBS (pH 7.2-7.4), if cell concentration is greater than 1 million/ml. Damage the cells by repeated freeze-thaw cycles to release intracellular components. Centrifuge for 20-min at 2000-3000 rpm. If precipitation appears, centrifuge again.
- Tissue Samples- Rinse tissues in PBS (pH 7.4) to remove excess blood thoroughly and weigh before homogenization. Mince tissues and homogenize them in PBS (pH7.4) with a glass homogenizer on ice. Thaw at 2-8°C or freeze at -20°C. Centrifuge at 2000-3000 RPM for approximately 20 minutes and collect the supernatant carefully.
Note: Grossly hemolyzed samples are not suitable for use in this assay