Abstract The objective of this study was to investigate the effects of dietary zinc deficiency and protein-energy malnutrition (PEM), alone and in combination, on murine splenic T-lymphocyte subpopulations and cell cycle progression using flow cytometry. Four month old C56BL/6 female mice were fed Zn-deficient (ZnDF), low protein (LP), combined Zn-deficient and low protein (ZnDF&LP), energy-restricted (ER) or control (CTRL) diet for 4 weeks. The CD4+/CD8+ ratio of T lymphocytes was not altered by the deficient diets, however, the total percentage of CD4+ plus CD8+ cells within the CD3+ population was less in all deficient groups compared to the CTRL group. When spleen cells were stimulated with concanavalin A (ConA) in the presence of 2-mercaptoethanol, the ZnDF&LP, ZnDF and LP groups had significantly fewer cells in both early and late S phase and significantly more cells in the G0 or resting state than the CTRL group. The ER group had significantly fewer cells in total S phase than the CTRL group. These...