Primary murine CD4+ T cells fail to acquire the ability to produce effector cytokines when active Ras is present during Th1/Th2 differentiation.
Constitutive Ras signaling has been shown to augment IL-2 production, reverse anergy, and functionally replace many aspects of CD28 co-stimulation in CD4+ T cells. These data raise the possibility that introduction of active Ras into primary T cells might result in improved functionality in pathologic situations of T cell dysfunction, such as cancer or chronic viral infection. To test the biologic effects of active Ras in primary T cells, CD4+ T cells from Coxsackie-Adenovirus Receptor Transgenic mice were transduced with an adenovirus encoding active Ras. As expected, active Ras augmented IL-2 production in naive CD4+ T cells. However, when cells were cultured for 4 days under conditions to promote effector cell differentiation, active Ras inhibited the ability of CD4+ T cells to acquire a Th1 or Th2 effector cytokine profile. This differentiation defect was not due to deficient STAT4 or STAT6 activation by IL-12 or IL-4, respectively, nor was it associated with deficient induction of T-bet and GATA-3 expression. Impaired effector cytokine production in active Ras-transduced cells was associated with deficient demethylation of the IL-4 gene locus. Our results indicate that, despite augmenting acute activation of naïve T cells, constitutive Ras signaling inhibits the ability of CD4+ T cells to properly differentiate into Th1/Th2 effector cytokine-producing cells, in part by interfering with epigenetic modification of effector gene loci. Alternative strategies to potentiate Ras pathway signaling in T cells in a more regulated fashion should be considered as a therapeutic approach to improve immune responses in vivo.
Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America.
Sujit V
SV
Janardhan
Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America.
Reinhard
R
Marks
Department of Pathology, The University of Chicago, Chicago, Illinois, United States of America; Department of Medicine, The University of Chicago, Chicago, Illinois, United States of America.
Thomas F
TF
Gajewski
D000818:Animals; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology*; D062727:Coxsackie and Adenovirus Receptor-Like Membrane Protein / Q000235:genetics; D016207:Cytokines / Q000096:biosynthesis*; D004789:Enzyme Activation / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D051379:Mice; D008822:Mice, Transgenic; D060888:Real-Time Polymerase Chain Reaction; D018631:ras Proteins / Q000378:metabolism*
D062727:Coxsackie and Adenovirus Receptor-Like Membrane Protein; D016207:Cytokines; D018631:ras Proteins