A Delayed HIV Infection Model with the Homeostatic Proliferation of CD4^(+)T Cells

In this paper,we investigate a delayed HIV infection model that considers the homeostatic prolif-eration of CD4^(+)T cells.The existence and stability of uninfected equilibrium and infected equilibria(smaller and larger ones)are studied by analyzing the characteristic equation of the system.The intracellular delay does not affect the stability of uninfected equilibrium,but it can change the stability of larger positive equilibrium and Hopf bifurcation appears inducing stable limit cycles.Furthermore,direction and stability of Hopf bifur-cation are well investigated by using the central manifold theorem and the normal form theory.The numerical simulation results show that the stability region of larger positive equilibrium becomes smaller as the increase of time delay.Moreover,when the maximum homeostatic growth rate is very small,the larger positive equilibrium is always stable.On the contrary,when the rate of supply of T cells is very small,the larger positive equilibrium is always unstable.

PD-1^(+)and TIM-3^(+)T cells widely express commonγ-chain cytokine receptors in multiple myeloma patients,and IL-2,IL-7,IL-15 stimulation up-regulates PD-1 and TIM-3 on T cells

Background:Immune checkpoint ligand-receptor interactions appear to be associated with multiple myeloma(MM)progression.Simultaneously,previous studies showed the possibility of PD-1 and TIM-3 expression on T cells upon stimulation with commonγ-chain family cytokines in vitro and during homeostatic proliferation.The aim of the present work was to study the impact of homeostatic proliferation on the expansion of certain T cell subsets upregulating PD-1 and TIM-3 checkpoint molecules.Methods:The expression of CD25,CD122,CD127 commonγ-chain cytokine receptors,phosphorylated signal transducer and activator of transcription-5(pSTAT5)and eomesodermin(EOMES)was comparatively assessed with flow cytometry in PD-1-and TIM-3-negative and positive T cells before the conditioning and during the first post-transplant month in peripheral blood samples of MM patients.Results:Substantial proportions of PD-1-and TIM-3-positive T lymphocytes expressed commonγ-chain cytokine receptors and pSTAT5.Frequencies of cytokine receptor expressing cells were significantly higher within TIM-3+T cells compared to PD-1+TIM-3−subsets.Considerable proportions of both PD-1-/TIM-3-negative and positive CD8+T cells express EOMES,while only moderate frequencies of CD4+PD-1+/TIM-3+T cells up-regulate this transcription factor.Besides,the surface presence of CD25 and intranuclear expression of EOMES in CD4+T cells were mutually exclusive regardless of PD-1 and TIM-3 expression.The stimulation with commonγ-chain cytokines up-regulates PD-1 and TIM-3 during the proliferation of initially PD-1/TIM-3-negative T cells but fails to expand initially PD-1+and TIM-3+T cell subsets in vitro.Conclusions:Both PD-1 and TIM-3 expressing T cells appear to be able to respond to homeostatic cytokine stimulation.Differences in commonγ-chain cytokine receptor expression between PD-1+and TIM-3+T cells may reflect functional dissimilarity of these cell subsets.Checkpoint blockade appears to alleviate lymphopenia-induced proliferation of PD-1+T cells but may raise the possibility of immune-mediated adverse events.