Pneumocystis carinii glycoprotein A binds macrophage mannose receptors

D. M. O'Riordan, J. E. Standing, Andrew Harold Limper

Research output: Contribution to journalArticle

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Abstract

Pneumocystis carinii causes life-threatening pneumonia in patients with impaired immunity. Recent studies suggest that alveolar macrophages interact with P. carinii through macrophage mannose receptors. However, the ligand(s) on P. carinii that is recognized by these receptors has not been fully defined. P. carinii contains a major mannose-rich surface antigen complex termed glycoprotein A (gpA). It was therefore hypothesized that gpA binds directly to macrophage mannose receptors and mediates organism attachment to these phagocytes. To assess this gpA was purified from P. carinii by continuous-elution gel electrophoresis. 125-labeled gpA bound to alveolar macrophages in a saturable fashion. In addition, gpA binding was substantially inhibited by both α-mannan and EDTA, further suggesting that gpA interacts with macrophage mannose receptors. Macrophage membrane proteins capable of binding to gpA were isolated with a gpA-Sepharose column. A 165- kDa membrane-associated protein was specifically eluted from the gpA- Sepharose column with EDTA (20 mM). This protein was identified as the macrophage mannose receptor by immunoprecipitation with a polyclonal anti- mannose receptor antiserum. To further investigate the role of gpA in P. carinii-macrophage interactions. 51Cr-labeled P. carinii cells were incubated with macrophages in the presence of increasing concentrations of soluble gpA, and organism attachment was quantified. Soluble gpA (2.5 mg/dl) competitively inhibited P. carinii attachment to alveolar macrophages by 51.3% ± 3.7% (P = 0.01). Our findings demonstrate that gpA present on P. carinii interacts directly with mannose receptors, thereby mediating organism attachment to alveolar macrophages.

Original languageEnglish (US)
Pages (from-to)779-784
Number of pages6
JournalInfection and Immunity
Volume63
Issue number3
StatePublished - 1995

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Pneumocystis carinii
Glycoproteins
Macrophages
Alveolar Macrophages
Edetic Acid
mannose receptor
Sepharose
Membrane Proteins
Mannans
Surface Antigens
Phagocytes
Mannose
Immunoprecipitation
Protein Binding
Electrophoresis
Immune Sera
Immunity

ASJC Scopus subject areas

  • Immunology

Cite this

Pneumocystis carinii glycoprotein A binds macrophage mannose receptors. / O'Riordan, D. M.; Standing, J. E.; Limper, Andrew Harold.

In: Infection and Immunity, Vol. 63, No. 3, 1995, p. 779-784.

Research output: Contribution to journalArticle

O'Riordan, D. M. ; Standing, J. E. ; Limper, Andrew Harold. / Pneumocystis carinii glycoprotein A binds macrophage mannose receptors. In: Infection and Immunity. 1995 ; Vol. 63, No. 3. pp. 779-784.
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