Of interest, from age 3 to 4 1/2 years, well before the molecular nature of the PAP was determined, we used inhaled and subcutaneous recombinant GM-CSF ( Figure  2B) . A transient increase in peripheral blood eosinophils up to 17% of the neutrophils occurred [18] (data not shown), but clearly no improvement of the alveolar proteinosis (Figure 2A, B, Figure 4C , D). Due to the expectations of the treating physicians, the intervals between consecutive therapeutic WLL were increased during GM-CSF treatment: In parallel, this was associated with an increased load of protein, demonstrating a lack of an effect of GM-CSF treatment ( Figure 4C, D) .