Autoimmune Pulmonary Alveolar Proteinosis (aPAP): Comprehensive Research Report

1. Disease Information

Overview: Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare diffuse lung disease characterized by accumulation of surfactant-derived lipoproteinaceous material within alveoli and terminal bronchioles, caused by circulating neutralizing autoantibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF). It accounts for approximately 90% of all pulmonary alveolar proteinosis (PAP) cases, making it the dominant clinical form of the broader PAP syndrome ATS Journal, Trapnell et al.. The disease is now understood as "a myeloid cell dysfunction, abnormal pulmonary surfactant accumulation, and innate immune deficiency" driven by autoantibody neutralization of GM-CSF (Current Pulmonology Reports 2024).

Key identifiers: - Orphanet: ORPHA:747 (Orphanet; OLS/ORDO) - MONDO: MONDO:0012579 (autoimmune pulmonary alveolar proteinosis) — distinct from MONDO:0012580 (hereditary pulmonary alveolar proteinosis) (Monarch Initiative) - OMIM: 610910 — "Pulmonary Alveolar Proteinosis, Acquired" (OMIM) - ICD-10-CM: J84.01 — Alveolar proteinosis (ICD10Data) - GARD (NIH): Disease ID 7499 (GARD) — aggregates Orphanet, OMIM, and MONDO data

Synonyms: Acquired pulmonary alveolar proteinosis; primary autoimmune PAP; idiopathic PAP (older term, largely superseded now that the GM-CSF autoantibody mechanism is understood); aPAP.

Data derivation: Most published knowledge derives from aggregated disease-level resources — national/regional patient registries (notably Japanese nationwide cohorts), single- and multi-center case series, and a handful of randomized controlled/phase 3 trials (IMPALA, IMPALA-2) — rather than large-scale individual-level EHR mining, reflecting the disease's rarity.

2. Etiology

Primary cause: aPAP is caused by polyclonal, high-titer, neutralizing IgG autoantibodies directed against GM-CSF. These autoantibodies bind and block GM-CSF from engaging its receptor (CSF2RA/CSF2RB) on alveolar macrophages and other myeloid cells, abrogating GM-CSF-dependent alveolar macrophage terminal differentiation and surfactant catabolism (Nature Communications 2015; PMC8647160). Recent work shows that total autoantibody titer does not correlate with disease severity; rather, epitope specificity and binding affinity are the key determinants of pathogenicity — a 2026 Nature Communications study characterized "affinity- and epitope-dependent pathogenicity of GM-CSF autoantibodies" (Nature Communications 2026).

Genetic risk factors: A genome-wide association study of 198 Japanese aPAP patients versus 395 controls identified two independent MHC risk loci: - HLA-DRB1*08:03 (OR 5.2) — also associated with higher anti-GM-CSF antibody titers - HLA-DPβ1 epitope (OR 0.28, protective) (Nature Communications 2021, "Genetic determinants of risk in autoimmune pulmonary alveolar proteinosis"; PMC7884840).

However, this HLA association has not been consistently replicated: a separate study of 41 aPAP patients versus 1,000 ethnic-matched controls found no HLA association (PLOS ONE; PMC6405167), suggesting population-specific or study-power-dependent genetic architecture.

Environmental/lifestyle risk factors: - Age and cigarette smoking are established risk factors for aPAP; smoking and dust inhalation are hypothesized to accelerate onset (ATS Journal review). A case report documented fluctuating radiographic disease burden tracking with cigarette smoke exposure (PMC7170098). - Occupational/inhalational exposures (silica, aluminum dust) are more clearly linked to secondary PAP than to autoimmune PAP; in a German cohort, silica dust exposure was reported in 21% and aluminum dust in 18% of cases, though causal attribution to the autoimmune subtype specifically remains uncertain. - Vaping/e-cigarette exposure and vitamin E acetate have been reported in individual case reports of aPAP (PMC8521389).

Gene-environment interactions: The prevailing model is a "two-hit" framework — an HLA-conferred (or otherwise genetically determined) predisposition to break tolerance to GM-CSF, combined with an environmental trigger (inhalational exposure, infection, or another autoimmune process) that precipitates autoantibody production. This remains incompletely characterized mechanistically and is an area of active investigation.

Protective factors: No specific protective genetic or environmental factors are firmly established beyond the HLA-DPβ1 protective epitope noted above.

3. Phenotypes

Symptom onset and course: Onset is typically insidious/gradual in patients aged 20–50 years, though pediatric and elderly-onset cases occur (Orphanet; GARD).

Table (click to expand)

Phenotype	Frequency/notes	Suggested HPO term
Dyspnea (exertional progressing to rest)	Most common presenting symptom	HP:0002094 (Dyspnea)
Cough (dry or with whitish/frothy sputum)	Second most common symptom	HP:0012735 (Cough)
Fatigue	Common	HP:0012378 (Fatigue)
Weight loss	Occurs with disease progression	HP:0001824 (Weight loss)
Chest pain	Reported	HP:0100749 (Chest pain)
Low-grade fever	Reported, especially with superimposed infection	HP:0001945 (Fever)
Hemoptysis	Uncommon	HP:0002105 (Hemoptysis)
Crackles on auscultation	Fine bibasilar crackles common	HP:0030830 (Crackles)
Hypoxemia	Progressive with disease severity	HP:0012418 (Hypoxemia)
Cyanosis	Late/severe disease	HP:0000961 (Cyanosis)
Digital clubbing	Uncommon/atypical — its presence should prompt consideration of alternative or complicating diagnoses (e.g., fibrosis)	HP:0100759 (Clubbing)
Asymptomatic/incidental finding	Up to ~30% identified incidentally on imaging	—

Source: GARD, NORD, Cleveland Clinic, PMC12180566 "Dyspnea and Deception".

Severity and progression: Disease course is heterogeneous — ranging from spontaneous remission, to stable/indolent disease, to progressive respiratory failure. Severity correlates with radiographic burden (crazy-paving extent on HRCT), gas exchange parameters (PaO2, A-a gradient), and DLCO. Chinese multi-center cohorts have developed composite severity/prognosis scores (DSS, SPSP, and an updated SPSPII incorporating smoking status, symptoms, PaO2, %-predicted DLCO, and HRCT score) that outperform earlier single-parameter staging (PMC9941621).

Quality of life impact: Progressive dyspnea and fatigue substantially impair daily functioning; disease-specific QoL instruments are not well standardized in aPAP, and most QoL data come from case series rather than validated instruments (EQ-5D/SF-36 data are sparse in the primary literature).

4. Genetic/Molecular Information

Unlike hereditary PAP, autoimmune PAP is not a Mendelian genetic disease — no single causal gene mutation is required. However:

HLA-DRB1*08:03 and HLA-DPβ1 are associated risk/protective MHC alleles in at least one large Japanese GWAS (see Etiology, above) (Nature Communications 2021).
MUC1 gene polymorphisms are associated with serum KL-6 levels and degree of pulmonary dysfunction in PAP, acting as a modifier of the biomarker/severity relationship rather than a causal driver (PMC4841967).
The causal molecular lesion is autoantibody-mediated functional GM-CSF deficiency rather than a structural gene defect — functionally analogous to but molecularly distinct from hereditary PAP (CSF2RA/CSF2RB loss-of-function mutations; HGNC:2435/HGNC:2436) and to the original description of PAP as a state where "GM-CSF gene expression is normal but protein release is absent" in some contexts (PubMed 9412586).
Somatic vs. germline: The autoantibodies are a somatically generated (B-cell/plasma-cell derived), polyclonal humoral immune product — not a germline or somatic DNA lesion.
Relevant gene/protein identifiers: CSF2 (GM-CSF ligand, HGNC:2434), CSF2RA (HGNC:2435), CSF2RB (HGNC:2436), PPARG (HGNC:9236), ABCG1 (HGNC:14638), PU.1/SPI1 (HGNC:11241) — all implicated in the downstream signaling/lipid-clearance axis (see Mechanism, below).

Epigenetics: No well-established disease-specific epigenetic signature has been reported in the primary literature reviewed; this remains an evidence gap.

5. Environmental Information

Toxin/occupational exposures: Silica and aluminum dust are the most frequently implicated inhalational hazards in cohorts that include PAP broadly, though their causal role is more firmly established for secondary PAP than for the autoimmune subtype specifically.
Smoking: An established accelerant/risk factor, with case evidence of disease activity fluctuating with smoking exposure (PMC7170098).
Vaping/inhalant substance use: Case reports link vaping and chronic inhalant/substance abuse to PAP presentations, including one describing vitamin E-acetate-positive BAL fluid in a vaping-associated aPAP case (PMC8521389; PMC5828087).
Infectious agents: Infections are not established as causal triggers of aPAP itself, but the GM-CSF-autoantibody state independently and bidirectionally interacts with infection risk (see Mechanism/Diagnostics — opportunistic infection section). Notably, GM-CSF autoantibodies have been identified in patients presenting primarily with disseminated nocardiosis, cryptococcal meningitis, and disseminated mycobacterial infection, sometimes in the absence of overt PAP (PMC9552154; JACI 2024; J Clin Immunol 2024).

6. Mechanism / Pathophysiology

Causal chain (trigger → clinical manifestation):

Trigger/upstream: Loss of immune tolerance to GM-CSF (influenced by HLA-DRB1*08:03 and possibly environmental co-factors) → polyclonal B-cell production of high-affinity, epitope-specific neutralizing anti-GM-CSF IgG autoantibodies (Nat Commun 2026).
Molecular pathway disruption: Circulating autoantibodies bind and neutralize/clear serum and local GM-CSF, preventing engagement of the GM-CSF receptor (CSF2RA/CSF2RB heterodimer) on alveolar macrophages. GM-CSF receptor signaling normally operates through two concentration-dependent branches: at low ligand concentration, phosphorylation of receptor serine585 couples to 14-3-3/PI3K/Akt signaling; at high concentration, phosphorylation of tyrosine577 couples to STAT5- and Shc-dependent pathways driving macrophage survival, activation, and proliferation (review, PMC11241585).
Cellular consequence: Loss of GM-CSF signaling impairs alveolar macrophage terminal differentiation, in particular failure to upregulate PU.1 (SPI1) and PPAR-γ, which are required for the GM-CSF–PU.1–PPARγ–ABCG1 axis governing cholesterol/lipid efflux and surfactant lipid catabolism in alveolar macrophages (PMC8647160; ATS Journal mechanistic review). Disruption of this axis is described as "dysregulation of cholesterol export within alveolar macrophages," where cholesterol accumulation impedes surfactant clearance (Current Pulmonology Reports 2024).
Tissue-level consequence: Progressive accumulation of PAS-positive, lipid-rich (oil-red-O-positive) surfactant material within alveolar macrophages and free within alveolar spaces → alveolar filling, impaired gas exchange, and the radiographic "crazy-paving" pattern.
Downstream/organism-level: Restrictive-to-mixed physiology, hypoxemia, and in a subset of patients, secondary pulmonary fibrosis — hypothesized to result from chronic retained lipoproteinaceous material, silica co-exposure, and/or superimposed infection causing epithelial injury (ERS 2024, "Pulmonary fibrosis in patients with autoimmune pulmonary alveolar proteinosis"). Hyaluronan has also been implicated in the fibrogenic cascade in aPAP-associated fibrosis (PMC12440733).

Immune system involvement: aPAP is now conceptually framed as a combined autoimmune disease + acquired innate immunodeficiency: the same autoantibodies that drive alveolar macrophage dysfunction also impair GM-CSF-dependent functions in circulating neutrophils (phagocytosis, chemotaxis, microbicidal activity) and other myeloid cells, producing a state of susceptibility to opportunistic infection independent of overt lung disease severity (PMC8647160).

Cell types involved (Cell Ontology suggestions): - Alveolar macrophage — CL:0000583 - Type II pneumocyte (surfactant-producing) — CL:0002063 - Neutrophil — CL:0000775 - Plasma cell (autoantibody-producing) — CL:0000786

GO biological process suggestions: - Surfactant homeostasis — GO:0043129 - Macrophage differentiation — GO:0030225 - Cholesterol efflux — GO:0033344 - Regulation of phagocytosis — GO:0050764 - Humoral immune response — GO:0006959

Molecular profiling: Serum and BAL proteomic/biomarker studies (KL-6, SP-A, SP-D, CYFRA21-1, CEA, LDH) are the primary "omics" layer characterized to date (see Diagnostics, below); large-scale transcriptomic/single-cell atlases specific to aPAP alveolar macrophages are limited in the literature surfaced here and represent a research gap.

7. Anatomical Structures Affected

Primary organ: Lung (respiratory system), specifically the alveoli and terminal bronchioles — UBERON:0002048 (lung); UBERON:0002299 (alveolar system); UBERON:0001991 (pulmonary alveolus)
Secondary/systemic involvement: Because GM-CSF autoantibodies impair neutrophil function systemically, extrapulmonary sites of opportunistic infection occur — notably CNS (Nocardia and Cryptococcal CNS infection) and disseminated mycobacterial disease, representing a secondary/complication-driven organ involvement rather than primary pathophysiology.
Tissue/cell level: Alveolar epithelium (type II pneumocytes, surfactant source) and alveolar macrophages (the primary dysfunctional effector cell) — Cell Ontology terms above.
Subcellular level: Macrophage lysosomes/phagolysosomes (site of impaired surfactant lipid catabolism) — GO:0005764 (lysosome); mitochondria and lipid droplets in lipid-laden ("foamy") macrophages.
Localization/laterality: Diffuse, typically bilateral, often basal-predominant or perihilar "bat-wing" distribution on imaging; classically patchy with sharp demarcation between affected and unaffected lung ("geographic" distribution).

8. Temporal Development

Onset: Typically insidious in adults 20–50 years old; pediatric-onset and elderly-onset (including cases in the 70s–80s) reported, the latter sometimes overlapping in presentation with hereditary PAP work-up.
Progression: Variable — a substantial minority follow an indolent/stable course, some undergo spontaneous remission, and others progress to hypoxemic respiratory failure. Disease severity scoring systems (DSS, SPSP, updated SPSPII) stratify HRCT extent, PaO2, and DLCO to track progression (PMC9941621).
Complications over time: Pulmonary fibrosis develops in a variable proportion of patients over years of follow-up — reported rates range widely (1.4% with severe fibrotic respiratory failure in a 223-patient Japanese cohort, versus 26% with any fibrosis on CT at median 3.6 years follow-up in another cohort), reflecting differences in fibrosis definition/detection threshold across studies (ERS 2024).
Remission patterns: Both spontaneous and treatment-induced (post-WLL, post-GM-CSF therapy) remission are documented; relapse can occur, particularly if autoantibody titers/affinity remain elevated.

9. Inheritance and Population

Inheritance pattern: Not Mendelian — aPAP is an acquired autoimmune disease, though HLA-linked genetic susceptibility modifies risk (see Etiology).
Prevalence: Estimates vary substantially by region and case-ascertainment method:
Japan: ~1/38,000 (higher due to a national registry and greater case-finding) (NORD)
United States: ~1/150,000 (likely an underestimate due to underdiagnosis)
A separate cross-national estimate: PAP prevalence 6.87 ± 0.33 per million population overall, similar between sexes, increasing with age (Orphanet J Rare Dis 2018; PMC6069872)
A 2025 Japanese administrative claims database study provides updated national epidemiology (PubMed 39872388)
Sex ratio: Historically described with male predominance, though more recent population-level data suggest near-equal sex distribution once ascertainment bias is accounted for.
Age distribution: Peak presentation 20–50 years; pediatric and elderly-onset cases occur but are less common.
Founder effects/consanguinity/carrier frequency: Not applicable — these concepts apply to the hereditary (CSF2RA/CSF2RB) form, not autoimmune PAP.
Geographic distribution: No strong endemic geographic clustering reported beyond registry-driven detection differences (Japan's higher reported prevalence reflects a mature national PAP registry rather than a true regional excess).

10. Diagnostics

Imaging: High-resolution CT (HRCT) shows the classic "crazy-paving" pattern — ground-glass opacities with superimposed interlobular septal thickening — often with sharp geographic demarcation between affected and normal parenchyma (AJR; PMC5354367). Quantitative CT scoring correlates with pulmonary function test results.

Bronchoalveolar lavage (BAL): Usually diagnostic without biopsy. Lavage fluid is grossly milky/opaque; cytology shows large, foamy alveolar macrophages and extracellular eosinophilic proteinaceous material that is PAS-positive and Alcian-blue-negative, with oil-red-O-positive lipid content (StatPearls; Hindawi CRJ 2016).

Serologic diagnosis: Elevated serum anti-GM-CSF autoantibody titer (typically measured by ELISA) is considered diagnostic/confirmatory for the autoimmune subtype and distinguishes it from hereditary and secondary PAP.

Serum biomarkers (disease activity/monitoring): - KL-6 (high-molecular-weight MUC1 mucin) — elevated in serum and BAL in most aPAP patients, correlates with disease activity, decreases post-WLL, and is a validated predictor of outcome/mortality (Orphanet J Rare Dis 2013; PMC3629718). MUC1 polymorphisms modify baseline KL-6 levels (PMC4841967). - SP-A and SP-D (surfactant proteins) — elevated; SP-A/SP-D show transient post-WLL rises distinct from KL-6's decline pattern. - CYFRA21-1 — reported as a more sensitive severity biomarker than some traditional markers (PMC8725332). - LDH, CEA, CA15-3, NSE — correlate positively with disease severity score and A-a gradient in Chinese cohort studies.

Genetic/molecular testing: Not required for diagnosis of the autoimmune form per se, but CSF2RA/CSF2RB sequencing is used to exclude hereditary PAP, particularly in atypical-age presentations or when anti-GM-CSF antibodies are unexpectedly negative.

Suggested LOINC/SNOMED considerations: BAL cytology PAS stain, serum KL-6 assay, and anti-GM-CSF antibody assay are the key laboratory studies; specific LOINC codes should be confirmed against local lab compendia at curation time.

Differential diagnosis: Hereditary PAP (CSF2RA/CSF2RB mutation, GM-CSF-antibody-negative, earlier onset), secondary PAP (hematologic malignancy, immunodeficiency, chronic infection, pneumotoxic exposure — macrophage number/function reduced by an underlying condition rather than autoantibody-mediated), other interstitial lung diseases with ground-glass/crazy-paving patterns (e.g., NSIP, organizing pneumonia, lipoid pneumonia, PJP pneumonia).

Complications requiring diagnostic vigilance: Because of the associated innate immune deficiency, clinicians are advised to maintain a high index of suspicion for opportunistic infection (Nocardia, Cryptococcus, nontuberculous/tuberculous mycobacteria) in patients with elevated GM-CSF autoantibodies, even in the absence of classic PAP radiographic findings (Open Forum Infect Dis 2022).

11. Outcome/Prognosis

Survival: Approximately 80% five-year survival with treatment (GARD/NORD estimates). Disease course ranges from spontaneous remission through chronic stable disease to death from respiratory failure or secondary infection.
Mortality drivers: Progressive hypoxemic respiratory failure; secondary pulmonary fibrosis (a "rare but potentially life-threatening complication," with severe fibrotic respiratory failure in ~1.4% of a 223-patient Japanese cohort); opportunistic infection (disseminated nocardiosis, cryptococcal meningitis, mycobacterial disease) related to the GM-CSF-antibody-driven innate immune defect.
Prognostic biomarkers: Serum KL-6 is a validated predictor of outcome (PMC3629718); composite severity scores (DSS/SPSP/SPSPII incorporating HRCT score, PaO2, %-predicted DLCO, smoking status) predict prognosis and treatment response in Chinese multi-center cohorts (PMC9941621).
Recovery potential: WLL and GM-CSF augmentation therapy substantially improve gas exchange and reduce disease burden; complete resolution occurs in only ~30% with WLL alone, improved further by combination with inhaled GM-CSF therapy.
COVID-19 interaction: A single-center study specifically examined outcomes of COVID-19 infection in aPAP patients, relevant given the innate immune deficiency component of the disease (PMC10638736).

12. Treatment

First-line — Whole Lung Lavage (WLL): Remains the standard of care; performed under general anesthesia, sequential lavage of each lung with large-volume saline to mechanically remove accumulated surfactant material. WLL alone achieves complete resolution in only ~30% of patients (CHEST/journal.chestnet.org). NCIT suggestion: therapeutic bronchoalveolar lavage procedure (closest available NCIT clinical-intervention term should be verified via OAK, e.g. under Therapeutic Procedure NCIT:C49236).

GM-CSF augmentation therapy (pharmacotherapy, pathogenesis-driven): - Inhaled sargramostim (recombinant human GM-CSF) — restores alveolar macrophage GM-CSF signaling/function locally, bypassing circulating neutralizing antibodies to some degree. A phase II randomized trial showed inhaled sargramostim following WLL reduced need for repeat WLL, improved lung function, and was safe and more effective than WLL alone (PubMed 37973175; NEJM 2019). - Inhaled molgramostim (recombinant GM-CSF, Savara Inc.) — the most advanced pharmacotherapy in development: - Phase 2/3 IMPALA trial: NEJM 2020 (NEJM) - Phase 3 IMPALA-2 trial (164 patients, 300 μg once daily × 48 weeks): significantly greater improvement in DLCO (hemoglobin-adjusted, % predicted at week 24, primary endpoint) versus placebo (NEJM 2025; PubMed 40834301; plain-language summary) - Regulatory status (as of the search date): BLA (brand name Molbreevi) submitted to FDA December 2025; PDUFA target action date extended to November 22, 2026; an FDA-permitted Early Access Program has been running since September 2024 (Drugs.com; CHEST Physician). Not yet FDA-approved at time of this report.

Refractory disease (per ERS treatment sequencing): 1. WLL 2. Inhaled GM-CSF 3. Rituximab (anti-CD20 B-cell depletion, typically 1000 mg × 2 doses two weeks apart) — reduces anti-GM-CSF titers, improves oxygenation, decreases WLL frequency 4. Plasmapheresis — case-level evidence of reduced anti-GM-CSF antibody levels (e.g., 24.8 → 2.7 mcg/mL after a 5-day protocol) correlating with reduced WLL need, improved DLCO, and symptomatic benefit, though responses are inconsistent across reported cases; some patients remain refractory to both rituximab and plasmapheresis despite antibody reduction (PMC8818429; PubMed 25557091) (Drugs journal 2025, pharmacotherapy review)

Advanced/last-resort: Lung transplantation for suitable patients with severe disease refractory to all other therapies; notably, PAP recurrence post-transplant has been reported (PMC7199162).

Suggested NCIT terms: - Rituximab — NCIT:C1197 (verify via OAK) - Plasmapheresis — closest NCIT therapeutic-procedure term (verify) - Lung transplantation — NCIT:C15289 (Organ Transplantation) - Pharmacotherapy (generic, for GM-CSF biologics) — NCIT:C15986, with therapeutic_agent bound to sargramostim/molgramostim (CHEBI or NCIT drug term — verify exact identifiers via OAK before curation)

Emerging/experimental: Pulmonary macrophage transplantation has shown efficacy in preclinical (murine Csf2ra−/−) models of hereditary PAP and is conceptually relevant as a future cell-therapy direction, though this is currently demonstrated in the hereditary rather than autoimmune model system.

13. Prevention

No established primary prevention (e.g., vaccination) exists for aPAP, as the autoimmune trigger is not fully characterized. Reasonable extrapolated measures based on identified risk factors: - Smoking cessation counseling — since smoking is an established risk/aggravating factor - Avoidance of inhalational occupational hazards (silica, aluminum dust) where feasible, particularly relevant to reducing secondary-PAP risk and possibly aPAP severity/fibrosis progression - Secondary prevention/surveillance: Given the innate immune deficiency, clinicians monitoring known aPAP or GM-CSF-autoantibody-positive patients should maintain heightened surveillance for opportunistic infection (Nocardia, Cryptococcus, mycobacteria), enabling earlier detection and treatment of disseminated infection. - Genetic counseling: Not applicable in the classic sense (non-Mendelian), though differentiating from hereditary PAP is relevant for family counseling when hereditary PAP is in the differential.

14. Other Species / Natural Disease

Naturally occurring autoimmune PAP driven by spontaneous anti-GM-CSF autoantibodies has not been robustly documented as a natural veterinary disease in the literature surfaced by this search; PAP-like presentations in animals are more typically studied via engineered genetic models (below) rather than spontaneous autoimmune disease.
Comparative biology of the GM-CSF/alveolar macrophage axis is well conserved across mammals, underpinning the utility of mouse models (below).

15. Model Organisms

GM-CSF-deficient (Csf2−/−) mice: The original and foundational model. GM-CSF knockout mice spontaneously develop a PAP-like phenotype due to defective surfactant clearance from failure of alveolar macrophage terminal differentiation, closely paralleling human PAP pathology, with impaired innate immunity to pulmonary pathogens as a shared feature (BMC Immunology 2013, "mixed M1/M2 phenotypes").

Csf2ra−/− mice (hereditary PAP model, mechanistically relevant to the shared downstream pathway): A more recent, refined murine model in which macrophages cannot bind or signal through GM-CSF, exhibiting functional defects in phagocytosis, cholesterol clearance, and surfactant clearance; mice develop time-dependent, progressive lung disease closely paralleling human hereditary PAP clinical, physiological, histopathological, biochemical, and biomarker features (Am J Physiol Lung Cell Mol Physiol 2021). This model has been used to test pulmonary macrophage transplantation (PMT) without myeloablation, achieving long-term engraftment and durable restoration of GM-CSF responsiveness over 6 months of follow-up.

Humanized IL-3/GM-CSF knock-in mice: Engineered to express human IL-3/GM-CSF, supporting human alveolar macrophage development and human immune responses in the lung — a translational bridge model for studying human myeloid biology in vivo (PNAS 2011; PMC3038773).

Model limitations: None of these genetic models fully recapitulates the autoimmune (autoantibody-driven, HLA-associated) etiology of human aPAP — they model the shared downstream GM-CSF-signaling-loss pathophysiology rather than the upstream autoimmune breakdown of tolerance. A true autoantibody-mediated aPAP model (e.g., passive transfer of anti-GM-CSF antibodies, or an induced-autoimmunity model) was not identified as a well-established standard model in this search and represents a documented modeling gap — relevant to a HUMAN_MODEL_MISMATCH framing if curated into a mechanistic knowledge base, since model organisms recapitulate the surfactant-clearance/macrophage-dysfunction phenotype but not the autoimmune trigger itself.

Resources: MGI (Mouse Genome Informatics) for Csf2/Csf2ra/Csf2rb knockout allele records; IMPC/KOMP for conditional/knockout mouse line availability.

Summary of Suggested Ontology Terms for Curation

Table (click to expand)

Category	Term
Disease	MONDO:0012579 (autoimmune PAP); ORPHA:747; OMIM:610910; ICD-10-CM:J84.01
Related/differential disease	MONDO:0012580 (hereditary PAP)
Causal gene/protein (ligand)	CSF2 / GM-CSF, HGNC:2434
Receptor genes	CSF2RA (HGNC:2435), CSF2RB (HGNC:2436)
Downstream TFs/transporters	SPI1/PU.1 (HGNC:11241), PPARG (HGNC:9236), ABCG1 (HGNC:14638)
Key phenotype (HP)	Dyspnea HP:0002094; Cough HP:0012735; Hypoxemia HP:0012418; Crackles HP:0030830
Key cell types (CL)	Alveolar macrophage CL:0000583; Type II pneumocyte CL:0002063; Neutrophil CL:0000775
Key anatomy (UBERON)	Lung UBERON:0002048; Pulmonary alveolus UBERON:0001991
Key GO processes	Surfactant homeostasis GO:0043129; Macrophage differentiation GO:0030225; Cholesterol efflux GO:0033344
Treatments (NCIT, verify via OAK before use)	Pharmacotherapy NCIT:C15986; Organ Transplantation NCIT:C15289

(All ontology term IDs above should be independently verified against the live OAK adapters before insertion into any dismech YAML entry, per project SOP — this report is a research input, not pre-validated curation content.)

Notes on Evidence Gaps

No MONDO/Orphanet-listed formal ICD-11 mapping was independently confirmed in this pass (ICD-10-CM J84.01 was confirmed; the ICD-11 equivalent should be separately verified).
Precise 5-year survival and mortality figures come from patient-advocacy/aggregator summaries (NORD/GARD) rather than a single primary epidemiological study with a directly quotable abstract sentence — a primary-source survival curve (e.g., from a national registry cohort paper) should be sourced and quoted verbatim before use as curated evidence.
A dedicated autoantibody-mediated (rather than genetic-knockout) mouse/model-organism system for aPAP was not identified; this is a genuine translational gap, not a search omission.
HLA association findings are population-inconsistent (positive in one Japanese GWAS, negative in another cohort) — this contradiction should be preserved as a KNOWLEDGE_GAP/nuanced etiology claim rather than flattened to a single "HLA-DRB1*08:03 causes aPAP" statement.