Human alveolar macrophages present antigen ineffectively due to defective expression of B7 costimulatory cell surface molecules

J Clin Invest. 1995 Mar;95(3):1415-21. doi: 10.1172/JCI117796.


Alveolar macrophages, resident phagocytic cells in the lung that derive from peripheral blood monocytes, are paradoxically ineffective in presenting antigen to T cells. We found that antigen presentation by alveolar macrophages could be restored by the addition of anti-CD28 mAb to cultures of T cells and macrophages, indicating that costimulation by alveolar macrophages via the CD28 pathway was defective. In addition, we found that alveolar macrophages activated with IFN-gamma failed to express B7-1 or B7-2 antigens, which normally ligate CD28 on T cells and provide a costimulatory signal required for the activation of T cells. These observations are the first to demonstrate the inability of a "professional" antigen-presenting cell type to effectively express the costimulatory molecules B7-1 and B7-2. Inasmuch as immune reactions within the lung are inevitably associated with inflammatory injury to pulmonary tissue, these observations suggest that reduced expression of B7-1 and B7-2 by alveolar macrophages may be advantageous, as a critical mechanism involved in the induction of peripheral tolerance to the abundance of antigens to which mucosal tissues are continuously exposed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Antigen Presentation / immunology*
  • Antigen-Presenting Cells / immunology
  • Antigens, CD*
  • B7-1 Antigen / biosynthesis*
  • B7-2 Antigen
  • CD28 Antigens / immunology
  • Cells, Cultured
  • Female
  • Humans
  • Interleukin-10 / immunology
  • Interleukin-12 / immunology
  • Lung / immunology*
  • Lymphocyte Activation
  • Macrophages, Alveolar / immunology*
  • Male
  • Membrane Glycoproteins / biosynthesis*
  • T-Lymphocytes / immunology


  • Antigens, CD
  • B7-1 Antigen
  • B7-2 Antigen
  • CD28 Antigens
  • CD86 protein, human
  • Membrane Glycoproteins
  • Interleukin-10
  • Interleukin-12