The present invention includes compositions and methods for treating an autoimmune disorder or a cancer in a subject in need thereof, the method comprising: administering an effective amount of a composition comprising an oligonucleotide that specifically binds a complementary sequence of the Interleukin-7 receptor (IL7R) pre-mRNA that influences splicing of exon 6, wherein the SM-ASO increases or decreases inclusion of exon 6 in IL7R pre-mRNAs and respectively decreases or increases expression of the soluble isoform of IL7R (sIL7R). In certain embodiments, the oligonucleotide is an antisense oligonucleotide (ASO), or a splice-modulating antisense oligonucleotide (SM-ASO).