In this open-label study, four participants with ALS received subcutaneous injections of low dose IL-2 (1 × 106 IU/injection/day) for 5 consecutive days every 2 weeks and one subcutaneous injection of CTLA4-Ig (125 mg/mL/injection) every 2 weeks coinciding with the first IL-2 injection of each treatment cycle. This evidence concerns the gene CTLA4 and amyotrophic lateral sclerosis.