- patients with known history of serious allergic reactions, including anaphylaxis, to human granulocyte-macrophage colony stimulating factor such as sargramostim, yeast-derived products, or any component of the product. - mechanical ventilation before start of study - patients with peripheral white blood cell count above 25.000 per microliter and/or active myeloid malignancy - patients on high dose systemic steroids (> 20 mg methylprednisolone or equivalent) - patients on lithium carbonate therapy - patients enrolled in another investigational drug study - pregnant or breastfeeding females (all female subjects regardless of childbearing potential status must have negative pregnancy test at screening) - patients with serum ferritin >2000 mcg/ml (which will exclude ongoing hlh)

- patients with known history of serious allergic reactions, including anaphylaxis, to human granulocyte-macrophage colony stimulating factor such as sargramostim, yeast-derived products, or any component of the product. - mechanical ventilation before start of study - patients with peripheral white blood cell count above 25.000 per microliter and/or active myeloid malignancy - patients on high dose systemic steroids (> 20 mg methylprednisolone or equivalent) - patients on lithium carbonate therapy - patients enrolled in another investigational drug study - pregnant or breastfeeding females (all female subjects regardless of childbearing potential status must have negative pregnancy test at screening) - patients with serum ferritin >2000 mcg/ml (which will exclude ongoing hlh)