This 2-sample MR investigation uncovered a total of 5 immunophenotypes, including CD25++ CD45RA+ CD4 not regulatory T cell %CD4+ T cell, CD25++ CD45RA+ CD4 not regulatory T cell %T cell, CD127 on CD28+ CD4+ T cell, CD4 on HLA DR+ CD4+ T cell and HLA DR on CD14− CD16+ monocyte might be positively associated with the risk of FS. Here, CD4 is linked to Feingold syndrome.