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Specific binding of surfactant apoprotein SP-A to rat alveolar macrophages

U Pison1, J R Wright, S Hawgood

  • 1Cardiovascular Research Institute, University of California, San Francisco 94143.

The American Journal of Physiology
|April 1, 1992
PubMed

Insights

Surfactant protein A (SP-A) binds to alveolar macrophages via a specific receptor. This interaction is mediated by SP-A's collagen-like domain, suggesting a key role in lung immunity.

Area of Science:

  • Pulmonary immunology
  • Cellular biology
  • Biochemistry

Background:

  • Surfactant protein A (SP-A) is crucial for lung immune function.
  • SP-A's interaction with alveolar macrophages is known to influence their activity.
  • The precise mechanisms of SP-A binding to macrophages require further elucidation.

Purpose of the Study:

  • To investigate the binding characteristics of SP-A to rat alveolar macrophages.
  • To identify potential mediators and receptors involved in SP-A-macrophage interaction.
  • To understand the role of SP-A's collagen-like domain in this binding.

Main Methods:

  • Radiolabeling of SP-A with iodine-125 (125I).
  • In vitro binding assays using rat alveolar macrophages at 4°C.
  • Saturation binding analysis and competition assays with unlabeled SP-A, C1q, type V collagen, and bovine serum albumin.

Main Results:

  • SP-A binding to alveolar macrophages was found to be saturable.
  • Half-maximal binding occurred at a SP-A concentration of 4 µg/ml.
  • Binding was competitively inhibited by unlabeled SP-A, C1q, and type V collagen, but not by bovine serum albumin.

Conclusions:

  • The interaction between SP-A and alveolar macrophages involves specific binding.
  • SP-A's collagen-like domain appears to mediate a significant component of this interaction.
  • These findings suggest the presence of a specific SP-A receptor on alveolar macrophage surfaces.

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