SPA ELISA Kit (Pulmonary Surfactant Associated Protein A)

Full Name: SPA ELISA Kit (Pulmonary Surfactant Associated Protein A)
Reactivity: Human
Sample Type: Plasma, Tissue Homogenates, Serum, Biological Fluids
Sensitivity: 9.375 pg/ml


Surfactant protein A (SP-A) refers to a large multimeric collectin and C-type lectin important for pulmonary immune defenses and surfactant homeostasis regulating surface tension in the alveoli air-liquid interface. As part of the surfactant layer coating alveolar surfaces, SP-A participates in complex organizational dynamics while additionally functioning as an opsonin mediating pathogen interactions with patrolling alveolar macrophages. Thereby SP-A holds duties spanning biophysical surfactant functionality and host immunity intrinsic to lung health.

As the most abundant surfactant apoprotein by mass, SP-A integrates into the layer-structured film via its collagen-like N-terminal domain while the globular C-type lectin domain interacts with resident alveolar macrophages and inhaled microbes. By binding carbohydrates on bacterial, fungal and viral pathogens, SP-A acts as opsonin to enhance phagocytic clearance as part of early innate lung defenses. Additionally, SP-A interacts with various immune cell receptors to modulate downstream inflammation both activating and suppressing effects contingent on specific signaling contexts. Hence, surfactant protein-A sits at the crux coordinating surfactant structure-function dynamics and immune tolerogenicity necessary within continuously ventilated delicate alveoli.

However, leakage of SP-A into systemic circulation signifies lung injury as levels increase in settings of infection, inflammation and permeability disruption. Furthermore, deficiency in functional SP-A arises in certain genetic disorders and respiratory distress syndrome in premature infants due to inadequate surfactant processing. This compromises both surface-tension lowering biophysical functionality as well as immune defenses heightening risks in these vulnerable populations.


Human SPA ELISA kit can measure concentrations of pulmonary surfactant associated protein A (SPA, SFPA1, COLEC4, PSAP, SP-A, collectin-4, alveolar proteinosis protein) present is plasma, serum, biological fluids or tissue homogenate samples.


All reagents supplied need to be stored at 2 °C – 8 °C, unopened reagents will retain reactivity until expiration date. Do not use reagents beyond this date.

  • One 96-Well Plate: Pre-coated with anti-SPA antibody.
  • Standards: Lyophilized recombinant.
  • Sample/Standard Dilution Buffer.
  • Biotinylated-labelled Antibody.
  • Antibody Dilution Buffer.
  • HRP-Streptavidin Conjugate (SABC).
  • SABC Dilution Buffer.
  • TMB Substrate.
  • Wash Buffer (25x).
  • Plate Sealer.
  • Product Instructions.


For this SPA ELISA kit, it is recommended that a standard curve is generated for each assay carried out.

Standard Curve: 0, 15.625, 31.25, 62.5, 125, 250, 500, 1000 pg/ml.
Reactivity: Human
Sensitivity: 9.375 pg/ml
Range: 15.625 – 1000 pg/ml
Principle: Sandwich, Double Antibody
Application: Research Use Only.


– Specificity: Highly specific for SPA, no cross reactivity or interference between SPA and analogues was detected.
– Recovery: Serum (89 – 102%), EDTA Plasma (90 – 98%), Heparin Plasma (93 – 103%).
– Linearity: Serum (85 – 103%), EDTA Plasma (82 – 101%), Heparin Plasma (80 – 95%).
– Precison Intra-Assay: CV < 8%
– Precison Inter-Assay: CV < 10%


  1. Surfactant protein A: A key player in lung homeostasis. Int J Biochem Cell Biol. (2016) 81 (Pt A): 151-155. Nathan N., et al.
  2. Native supramolecular protein complexes in pulmonary surfactant: Evidences for SP-A/SP-B interactions. J Proteomics. (2019) 207: 103466. Martínez-Calle M., et al.
  3. Alteration of surfactant protein A expression in renal cell carcinoma. Biotech Histochem. (2018) 93 (7): 519-525. Bassorgun CI., et al.


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