Material

Immunity declines during aging, however the mechanisms involved in this decline are not known. In this study, we show that cutaneous delayed type hypersensitivity (DTH) responses to recall antigens are significantly decreased in older individuals. However, this is not related to CC chemokine receptor 4, cutaneous lymphocyte-associated antigen, or CD11a expression by CD4+ T cells or their physical capacity for migration. Instead, there is defective activation of dermal blood vessels in older subject that results from decreased TNF-α secretion by macrophages. This prevents memory T cell entry into the skin after antigen challenge. However, isolated cutaneous macrophages from these subjects can be induced to secrete TNF-α after stimulation with Toll-like receptor (TLR) 1/2 or TLR 4 ligands in vitro, indicating that the defect is reversible. The decreased conditioning of tissue microenvironments by macrophage-derived cytokines may therefore lead to defective immunosurveillance by memory T cells. This may be a predisposing factor for the development of malignancy and infection in the skin during aging.

Naturally occurring CD4 + CD25 hi Foxp3 + Tregs (nTregs) are highly proliferative in blood. However, the kinetics of their accumulation and proliferation during a localized antigen-specific T cell response is currently unknown. To explore this, we used a human experimental system whereby tuberculin purified protein derivative (PPD) was injected into the skin and the local T cell response analyzed over time. The numbers of both CD4 + Foxp3 -(memory) and CD4 + Foxp3 + (putative nTreg) T cells increased in parallel, with the 2 populations proliferating at the same relative rate. In contrast to CD4 + Foxp3 -T cell populations, skin CD4 + Foxp3 + T cells expressed typical Treg markers (i.e., they were CD25 hi , CD127 lo , CD27 + , and CD39 + ) and did not synthesize IL-2 or IFN-γ after restimulation in vitro, indicating that they were not recently activated effector cells. To determine whether CD4 + Foxp3 + T cells in skin could be induced from memory CD4 + T cells, we expanded skin-derived memory CD4 + T cells in vitro and anergized them. These cells expressed high levels of CD25 and Foxp3 and suppressed the proliferation of skin-derived responder T cells to PPD challenge. Our data therefore demonstrate that memory and CD4 + Treg populations are regulated in tandem during a secondary antigenic response. Furthermore, it is possible to isolate effector CD4 + T cell populations from inflamed tissues and manipulate them to generate Tregs with the potential to suppress inflammatory responses. IntroductionNaturally occurring CD4 + CD25 hi Foxp3 + Tregs (nTregs) can prevent reactivity to both self and non-self antigens (1-4). Although early studies suggested that these cells are generated as a distinct population in the thymus, CD4 + CD25 hi Foxp3 + Tregs, which are phenotypically and functionally identical to the thymus-derived population, can also be generated after antigen-induced proliferation of CD4 + T cells in peripheral tissues in mice (5, 6). The rapid division of CD4 + CD25 hi Foxp3 + Tregs that has been shown to occur in vivo in mice (7) and humans (8) may be a mechanism for maintaining nTregs. This has particularly important implications for the lifelong maintenance of human Tregs after thymic involution, since CD4 + CD25 hi Foxp3 + T cells in humans have limited capacity for extensive self-renewal, due to short telomeres, and lack telomerase activity (8). It is important to consider the possible difference in behavior and characteristics of nTregs in mice and humans, especially given the potential for species-specific differences that might lead to side effects during therapy (9).The regulation of immunity and pathology by intervention at the Treg axis has been very successful in animal models, where it has been shown that CD4 + CD25 hi Foxp3 + T cells can be harnessed to prevent autoimmunity (10, 11), inflammatory disease (12),

BackgroundImmunity decreases with age, which leads to reactivation of varicella zoster virus (VZV). In human subjects age-associated immune changes are usually measured in blood leukocytes; however, this might not reflect alterations in tissue-specific immunity.ObjectivesWe used a VZV antigen challenge system in the skin to investigate changes in tissue-specific mechanisms involved in the decreased response to this virus during aging.MethodsWe assessed cutaneous immunity based on the extent of erythema and induration after intradermal VZV antigen injection. We also performed immune histology and transcriptomic analyses on skin biopsy specimens taken from the challenge site in young (<40 years) and old (>65 years) subjects.ResultsOld human subjects exhibited decreased erythema and induration, CD4+ and CD8+ T-cell infiltration, and attenuated global gene activation at the site of cutaneous VZV antigen challenge compared with young subjects. This was associated with increased sterile inflammation in the skin in the same subjects related to p38 mitogen-activated protein kinase–related proinflammatory cytokine production (P < .0007). We inhibited systemic inflammation in old subjects by means of pretreatment with an oral small-molecule p38 mitogen-activated protein kinase inhibitor (Losmapimod; GlaxoSmithKline, Brentford, United Kingdom), which reduced both serum C-reactive protein levels and peripheral blood monocyte secretion of IL-6 and TNF-α. In contrast, cutaneous responses to VZV antigen challenge were increased significantly in the same subjects (P < .0003).ConclusionExcessive inflammation in the skin early after antigen challenge retards antigen-specific immunity. However, this can be reversed by inhibition of inflammatory cytokine production that can be used to promote vaccine efficacy and the treatment of infections and malignancy during aging.

Reactivation of the varicella zoster virus (VZV) increases during aging. Although the effects of VZV reactivation are observed in the skin (shingles), the number and functional capacity of cutaneous VZV-specific T cells have not been investigated. The numbers of circulating IFN-γ-secreting VZV-specific CD4(+) T cells are significantly decreased in old subjects. However, other measures of VZV-specific CD4(+) T cells, including proliferative capacity to VZV antigen stimulation and identification of VZV-specific CD4(+) T cells with an major histocompatibility complex class II tetramer (epitope of IE-63 protein), were similar in both age groups. The majority of T cells in the skin of both age groups expressed CD69, a characteristic of skin-resident T cells. VZV-specific CD4(+) T cells were significantly increased in the skin compared with the blood in young and old subjects, and their function was similar in both age groups. In contrast, the number of Foxp3(+) regulatory T cells and expression of the inhibitory receptor programmed cell death -1 PD-1 on CD4(+) T cells were significantly increased in the skin of older humans. Therefore, VZV-specific CD4(+) T cells in the skin of older individuals are functionally competent. However, their activity may be restricted by multiple inhibitory influences in situ.

We investigated the relationship between varicella zoster virus (VZV) specific memory CD4+ T cells and CD4+Foxp3+ regulatory T cells (Tregs) that accumulate after intradermal challenge with a VZV skin test antigen. VZV-specific CD4+ T cells were identified with a MHC class II tetramer or by intracellular staining for either IFN-γ or IL-2 after antigen re-challenge in vitro. VZV-specific T cells, mainly of a central memory (CD45RA−CD27+) phenotype, accumulate at the site of skin challenge compared to the blood of the same individuals. This resulted in part from local proliferation since >50% of tetramer defined antigen-specific CD4+ T cells in the skin expressed the cell cycle marker Ki67. CD4+Foxp3+ T cells had the characteristic phenotype of Tregs, namely CD25hiCD127loCD39hi in both unchallenged and VZV challenged skin and did not secrete IFN-γ or IL-2 after antigenic re-stimulation. The CD4+Foxp3+ T cells from unchallenged skin had suppressive activity, since their removal led to an increase in cytokine secretion after activation. After VZV antigen injection, Foxp3+CD25hiCD127loCD39hi T cells were also found within the VZV tetramer population. Their suppressive activity could not be directly assessed by CD25 depletion since activated T cells in the skin were also CD25+. Nevertheless there was an inverse correlation between decreased VZV skin responses and proportion of CD4+Foxp3+ T cells present indicating indirectly, their inhibitory activity in vivo. These results suggest a linkage between the expansion of antigen-specific CD4+ T cells and CD4+ Tregs that may provide controlled responsiveness during antigen-specific stimulation in tissues.

This study assesses therapeutic efficacy of bleomycin delivered by dermojet in solely recalcitrant plantar warts. It provides preliminary evidence that this method of delivery may benefit a group of patients with particularly recalcitrant plantar warts and is safe and easy to use in routine dermatology practice.

No abstract