In this study we analyzed the impact of a MHC class-II-deficient environment on the differentiation of CD4+CD8- T lymphocytes into functional defined subsets of lymphokine-producing T-helper cells. To this end a CD4+CD8- T-cell line and CD4+CD8- T-cell clones, isolated from PBMCs of a type III BLS patient, were stimulated in vitro with anti-CD3 and PMA and assessed for lymphokine transcription patterns. The results of these analyses show that CD4+CD8- T cells that have matured in a MHC class-II-deficient environment display lymphokine transcription patterns that resemble those of MHC class-II-expressing family control-derived CD4+CD8- T cells.