This technology relates to the use of thymic stromal lymphopoietin (TSLP) to induce CD4+ T cell proliferation. This proliferation could be of particular relevance for patients in whom this cell population has been significantly reduced by HIV/AIDS or other conditions resulting in immunodeficiency. The proliferation of isolated CD4+ T cells can be induced through direct contact with TSLP or a nucleic acid encoding TSLP. The patent application also describes methods of inducing or enhancing an immune response through administration of CD4+ T cells that have been isolated and induced to proliferate using TSLP or a nucleic acid encoding TSLP. TSLPR knockout mice are also described in the patent application and available for licensing through a biological materials license agreement.