The development of severe immunodeficient mouse strains containing various human genes, including cytokines or HLA, has enabled the reconstitution of functional human immune systems after transplantation of human hematopoietic stem cells (HSC). Accumulating evidence has suggested that HLA-restricted antigen-specific human T-cell responses can be generated in these humanized mice. To directly monitor immune responses of human CD4(+) T cells, we introduced beta-lactoglobulin (BLG)-specific T cell receptor (TCR) genes derived from CD4(+) T-cell clones of cow-milk allergy patients into HSCs, and subsequently transplanted them into NOG-HLA-DR4 transgenic/I-A beta deficient mice (NOG-DR4/I-A degrees). In the thymus, thymocytes with BLG-specific TCR preferentially differentiated into CIM(+)CD8(-) single-positive cells. Adoptive transfer of mature CD4(+) T cells expressing the TCR into recipient NOG-DR4/I-A degrees mice demonstrated that human CD4(+) T cells proliferated in response to antigenic stimulation and produced IFN-gamma in vivo, suggesting that functional T-cell reactions (especially Th1-skewed responses) were induced in humanized mice. (C) 2014 Elsevier Inc. All rights reserved.