Single-Cell Analyses Reveal Two Defects in Peptide-Specific Activation of Naive T Cells from Aged Mice

Abstract

Confocal fluorescent microscopy was used to study redistribution of membrane-associated proteins in naive T cells from young and old mice from a transgenic stock whose T cells express a TCR specific for a peptide derived from pigeon cytochrome C. About 50% of the T cells from young mice that formed conjugates with peptide-pulsed APC were found to form complexes, at the site of binding to the APC, containing CD3ε, linker for activation of T cells (LAT), and Zap-70 in a central area and c-Cbl, p95vav, Grb-2, PLCγ, Fyn, and Lck distributed more uniformly across the interface area. Two-color staining showed that those cells that were able to relocalize c-Cbl, LAT, CD3ε, or PLCγ typically relocalized all four of these components of the activation complex. About 75% of conjugates that rearranged LAT, c-Cbl, or PLCγ also exhibited cytoplasmic NF-AT migration to the T cell nucleus. Aging had two effects. First, it led to a diminution of ∼2-fold in the proportion of T cell/APC conjugates that could relocalize any of the nine tested proteins to the immune synapse. Second, aging diminished by ∼2-fold the frequency of cytoplasmic NF-AT migration among cells that could generate immune synapses containing LAT, c-Cbl, or PLCγ. Thus naive CD4 T cells from old mice exhibit at least two separable defects in the earliest stages of activation induced by peptide/MHC complexes.

Aging, imbalanced inflammation and viral infection

“…Aging also impairs T-cell CD28 signaling 15 and immune synapse formation. 16 Furthermore, aging reduces T cell thymic output, leading to reduced numbers of naïve T cells, cells that are essential for eradicating infections from new pathogens. In addition, aging leads to an accumulation of memory T cells, 17 which are critical for prevention of re-infection and are the basis for vaccination therapies.…”

Age-Dependent Defects in TCR-Triggered Cytoskeletal Rearrangement in CD4+ T Cells

“…CH-12 cells pulsed with 20 g/ml of agonist or antagonist peptide were conjugated with CD4 ϩ T cells, as described (11). For the two-color analyses, we first used specific rabbit or mouse Abs to cytokeletal proteins (at 1 g/ml in PBS containing 0.2% BSA), or in some cases Alexa-488 phalloidin (at 2 U/ml in PBS/BSA), followed by biotin-GST-Grb2 (0.5 g/ml in PBS/BSA).…”

PD-1+memory phenotype CD4+T cells expressing C/EBPα underlie T cell immunodepression in senescence and leukemia

“…This may result in contraction of the T cell repertoire, leading to an increased incidence of poor responsiveness to new antigens (7). It also is recognized that CD4 ϩ T cells in the elderly are qualitatively altered, including a number of defects in the T cell receptor (TCR)-mediated signaling pathways, reduced immunologic synapse formation with antigenpresenting cells, diminished cognate helper function for B cells, and altered lymphokine production patterns (8)(9)(10)(11). These effects may be attributed primarily to the cellular changes in T cells rather than to the host environment (12).…”