We delivered exogenous murine recombinant (r)IL-4, as a long-acting formulation (complexed to rat anti-IL-4) into the peritonea of BALB/c SCID mice and determined that rIL-4 delivery +BmL3 infection was sufficient to recapitulate Mφ expansions and elevate arginase production in severe-combined immunodeficiency (Fig 3G–3I and S4 Fig). This evidence concerns the gene IL4 and severe combined immunodeficiency.