Although feasibility of the long term management of congenital PAP with WLL was demonstrated in this CD11b. The purity of neutrophils was greater than 95% as assessed by differential cell counts of Pappenheim cytospin preparations. Cell viability was greater than 95% using trypan-blue exclusion method. 106 neutrophils were treated with 50 ng/ml GM-CSF or the same volume of the vehicle buffer (aqua a.i.) for 30 min at 37°C. In the absence of GM-CSF stimulation, GM-CSF-Ra chain expression in the parents was only 50% of that of the controls ( Figure. 3 A) , whereas GM-CSF-Rb chain and CD11b expression were normal. After stimulation with GM-CSF, GM-CSF-Ra in the patient remained low, whereas the parents' level increased to almost control level. GM-CSF-Rb chain and CD11b stimulation were normal ( Figure. 3 A) . CD11b expression on the neutrophils was used to assess signal transduction after GM-CSF stimulation. In the patient, similar as blocked by auto-antibodies from a subject with auto-immune PAP, no dose-dependent stimulation of CD11b was observed, demonstrating interruption of signalling ( Figure. case of severe PAP, molecular diagnosing PAP as caused by a genetic deficiency of GM-CSFRa may have other important prophylactic and therapeutic implications. First, based on experiments in mice with PAP bone marrow transplantation may cure the disease [3] . Currently we believe however that the risks of a bone marrow transplant (chronic graft versus host disease, among others) outweigh its benefits (elimination of need for WLL). Second, if diagnosed early in a family with an index case, the opportunity of early intervention by lavages at times of good clinical condition will help to reduce complications.