Macrophages, GM-CSF and MARS Proteinosis

Pulmonary alveolar proteinosis (PAP) is a rare respiratory disease characterized by the accumulation of lipoproteinaceous material within the pulmonary alveoli, resulting in the majority of cases from a defective clearance of the surfactant by intra-alveolar macrophages.

Mutations in the MARS gene encoding methionyl-tRNA synthetase are responsible for a genetic form of alveolar proteinosis, but the pathophysiological mechanisms leading to mutations in the respiratory phenotype are not known.

The main hypothesis is that the alveolar proteinosis phenotype in these patients is secondary to a defective clearance of the surfactant by the alveolar macrophages.

The main objective of the study is to study the clearance capacity of lipoproteinaceous material by macrophages of patients with MARS related PAP. This will be investigate in cultured macrophages derived from peripheral blood monocytes of patients (patients with MARS related PAP) and controls (patients without MARS related PAP).

The subjects and the controls will be included during a hospitalization during which a blood sample and a bronchoscopy with broncoalveolar lavage must be performed as part of their care.

• Blood collection (Biological): 2 to 5 ml
• Bronchoalveolar lavage fluid collection (Biological): 5 to 25 ml

Primary outcomes

• Measurement of the clearance [Day 0]: Measurement of the clearance of abnormal lipo-proteinaceous material (from patients) at 48h of culture by cultured macrophages derived from peripheral blood monocytes from patients and controls. Microscopic examination of cell samples prepared on slide after cytospin and stained with oil red'O.

Secondary outcomes

• Measurement of the clearance after supplementation with methionine [Day 0]: Measurement of the clearance of abnormal lipo-proteinaceous material (from patients) at 48h culture with methionine supplementation in culture medium by cultured macrophages derived from peripheral blood monocytes from patients and controls. Microscopic examination of cell samples prepared on slide after cytospin and stained with oil red'O.
• Cellular phenotyping and study of the GM-CSF pathway [Day 0]: Description : Study the impact of mutations on the cell phenotype and the GM-CSF signalling pathway. (i) CD11b and CD49d cell immunostaining which are surface markers of healthy alveolar macrophages ; (ii) measurement of the level of intracellular phosphorylation of STAT5 by flow cytometry; and (iii) measurement of the level of expression of the SPI1, PPARγ and ABCG1 genes by quantitative PCR. These measurements will be performed in cultured macrophages derived from peripheral blood monocytes of patients and controls, but also in alveolar macrophages directly isolated from the BAL fluid of patients and controls. All these measurements will be performed in response to incubation with GM-CSF.

Sex: All, ages: any to 17 Years

Inclusion Criteria:

* Minors from 0 to 17 years hospitalized for their care at Necker Enfants Malades hospital and for whom a blood sample and a bronchoscopy with bronchoalveolar lavage must be performed as part of their care
* Information and consent of the holders of parental authority and the patient

Exclusion Criteria:

\- Refusal of holders of parental authority or patient

• Alice HADCHOUEL, Principal investigator, Assistance Publique - Hôpitaux de Paris