Effect of aging on epidermal dendritic cell populations in C57BL/6J mice

Tailoring cancer vaccines to the elderly: the importance of suitable mouse models

The incidence of cancer has increased over the last decade, mainly due to an increase in the elderly population. Vaccine therapy for cancer is potentially less toxic than chemotherapy or radiation and could, therefore, be especially effective in older, more frail cancer patients. However, it has been shown that older individuals do not respond to vaccine therapy as well as younger adults. This has been attributed to T cell unresponsiveness, a phenomenon also observed in cancer patients per se. Activation of tumor-specific T cells by cancer vaccines might be an approach, especially suitable for elderly patients, to eradicate or to prevent recurrence of tumors after primary treatment. To tailor pre-clinical testing of vaccine therapies to the elderly, it is important to have mouse models in which tumors develop at equivalent time points in their life span, as in humans. Such models are currently not available. This progress report first summarizes the current knowledge of tumor-immunological parameters potentially involved in T cell unresponsiveness in relation to aging in mice and humans. Secondly, it reviews those cancer vaccines that are known for their potential to induce tumor-specific T cell responses. Thirdly, it discusses the usefulness of currently available mouse models for pre-clinical testing of cancer vaccines applicable to the elderly population. Finally, experimental approaches are proposed, as to how to develop mouse models that allow the induction of specific tumors at will at different ages, expressing tumor-specific antigens in an 'immune competent' environment. These mouse models may teach us how to overcome immune deficits in the elderly, thereby facilitating the development of effective and safe cancer vaccines.

Dendritic cells in old age--neglected by gerontology?

Dendritic cells (DC) are known as the most efficient antigen-presenting cell type to activate T cells and are key modulators of the immune response. Due to their central role in immunology, DC have been considered as a useful tool for immunotherapy. They may also compensate failing T cell reactivity in aged persons. Despite numerous recent advances in the molecular and cell biology of DC, only very few groups have addressed the topic of DC and aging. It is the aim of the present contribution to give a short overview on what is known on DC in old age.

Surface markers and transendothelial migration of dendritic cells from elderly subjects

Age-related changes of immune functions have been extensively investigated in both humans and animal models; nevertheless, the literature on potential alterations of dendritic cells, potent antigen presenting cells responsible for initiating immune responses, with aging is very scarce. We studied the immuno-phenotype of peripheral blood dendritic cells of elderly and young subjects by three-color flow cytometry. In addition, the capacity of transendothelial migration, an important step in inflammatory reactions, of peripheral blood dendritic cells of elderly subjects was investigated in an in vitro model. The expression of HLA-DR in the peripheral blood dendritic cells of the elderly subjects was significantly decreased when compared to the young control subjects. The expression of various other surface markers was similar in the young and elderly subjects. The ability of transendothelial migration of dendritic cells was found to be unimpaired in the elderly subjects. Both in the young and elderly subjects a significantly higher expression of CD29, CD86, HLA-DR, and HLA-DQ in the dendritic cells that had migrated through the endothelium in comparison to nonadherent, nonmigrating cells was found. In the migrating dendritic cells of the elderly subjects a significantly increased expression of CD11c was observed, whereas the expression of CD54 was significantly enhanced in the migrating dendritic cells of the young subjects only. In conclusion, our results demonstrate intact functions and a normal immunophenotype of dendritic cells derived from elderly subjects. Dendritic cells thus seem to be functional and therefore are not responsible for the well-known decline of T cell functions with aging.

Unimpaired dendritic cells can be derived from monocytes in old age and can mobilize residual function in senescent T cells

Dendritic cells (DC) are powerful antigen presenting cells, which have the unique capacity to stimulate naive T cells. In spite of the well-known decline of T cell function in old age, little information is available on whether DC are also affected by the aging process. This is mainly due to problems with the isolation and purification of DC. Rapid progress in the characterization of DC has been made in recent years, as simple methods to generate large numbers of DC from precursors have been developed. It was the aim of the present study to compare monocyte derived DC from old and young healthy persons. The generation of DC from blood monocytes in response to GM-CSF and IL-4 treatment was similar in cells from young and old persons. The DC population thus obtained had a typical dendritic morphology and expressed DC surface markers, such as HLA class II, CD1a, CD11c, CD54, CD80 and CD86, but not CD14 for a period of up to three weeks in culture. DC from young and old persons produced IL-12 and TNF-alpha and responded equally well to maturation-inducing stimuli. DC maturation was stimulated by purified protein derivative (PPD) of Mycobacterium tuberculosis, whole inactivated influenza virus and by influenza split vaccine, but not by purified viral RNA. When tested for their antigen-presenting capacity, DC from young and old persons were capable of stimulating the proliferation and the cytokine production of T cells. It was of particular interest that CD45RA(+) as well as CD45RO(+) T cells from aged donors were unable to respond to stimulation with influenza proteins presented by monocytes, but were triggered to proliferate and to produce cytokines when antigen was presented by DC. The results demonstrate that DC from old persons (a) may still function as powerful antigen-presenting cells provided the right differentiation and maturation stimuli are present; (b) are capable of mobilizing residual capacity in senescent T cells and (c) may therefore represent a potent tool for immunotherapy and vaccines in old age.

Heterogeneous reactivity of murine epidermal Langerhans cells after application of FITC: a histochemical evaluation

To elucidate the detailed kinetics of epidermal Langerhans cells after topical contact sensitizer stimulation, we examined ATPase or Ia positive epidermal cells of BALB/c mice in a time-spaced manner after the topical application of fluorescein isothiocyanate (FITC). We also performed double labeling of Langerhans cells in epidermal sheets with ATPase activity and Ia antigen or costimulatory molecules (B7-1 and B7-2) after the same stimulation. Observations showed that the density of ATPase positive cells and Ia positive cells decreased following a different time course; the former reached a nadir (77.4% of control) at 4 h but the latter reached a minimum (82.8% of control) at 16 h after the application of FITC. A double labeling technique revealed an increase in Ia single positive cells at 4 h as opposed to that of ATPase single positive cells at 16 h after application. Both costimulatory molecules were expressed on the dendritic processes of many Langerhans cells as a dotty pattern at 4 h after application; B7 positive and ATPase negative areas were observed at this time. On electron microscopic observation, a few activated Langerhans cells found in the dermis at 4 h after application had distinctive profiles compared with residual Langerhans cells in the epidermis. These findings suggest that there is a heterogeneity of reactivity to FITC in epidermal Langerhans cells, and that only a small portion of them migrates from the epidermis during sensitization. The findings also indicate the importance of the interaction between the Langerhans cell and its surrounding microenvironment in the epidermis for its activation. In addition, the results indicate that the enzymatic and the phenotypic markers do not definitively reflect the presence (or absence) of Langerhans cells.

Primary and secondary alterations of immune reactivity in the elderly: impact of dietary factors and disease

The function of the immune system declines with age. It is the aim of the present review to demonstrate that it makes sense to distinguish between primary and secondary alterations of immune reactivity in the elderly. Primary changes occur as the result of an age-dependent intrinsic decline of immune responsiveness. They also occur in healthy persons, i.e. persons selected according to the criteria of the SENIEUR protocol of the European Community's Concerted Action Program on Aging (EURAGE). T lymphocytes are hereby more severely affected than B cells or antigen presenting cells, possibly due to the involution of the thymus, which is almost complete at the age of 60. Secondary immunological changes occur as the result of environmental factors including diet, drug intake, physical activity etc. or are alternatively due to underlying diseases. In this article, the effects of high lipid intake as well as the impact of diseases, such as for instance Alzheimer's disease and atherosclerosis, will be addressed. The results underline the complexity of immunological alterations to be expected in old age. Changes in the aging immune system represent an opportunity for increased frequency and severity of disease and endanger the protective effect of vaccination.

The aging immune system: primary and secondary alterations of immune reactivity in the elderly

The function of the immune system is known to decline in the elderly. The present communication will show that, similar to the situation in children, it is necessary to distinguish between primary and secondary alterations of the immune reactivity in the elderly. The primary immunological change in the elderly is the age-dependent intrinsic decline of immune responsiveness that is also observed in healthy persons, i.e., those selected according to the criteria of the SENIEUR Protocol of EURAGE (European Community Concerted Action on Aging). Secondary immunological changes are due to underlying diseases and various environmental factors, including diet, drug intake, physical activity, etc. While primary immunodeficiencies of the elderly are not, or only to a very minor extent, presently influenced by therapeutic measures, secondary alterations of the immune function offer further possibilities for corrective measures. Clinically, the consequences of impaired immune function in the elderly include increased susceptibility to infectious disease, the emergence of tumors, and increased autoimmune reactions, the latter albeit often without concomitant autoimmune disease. In fact, autoimmune diseases in generally begin to develop at younger ages, but their consequences are major factors affecting the quality of life of the elderly. Investigations of basic molecular and cellular aspects of the aging immune system are, therefore, of theoretical, clinical and socioeconomic interest.

Epidermal dendritic cell populations in the flaky skin mutant mouse

Flaky skin (gene symbol: fsn) is an autosomal recessive mouse mutation that causes pathologic changes in the skin yielding a papulosquamous disease resembling human psoriasis. Preliminary studies of epidermal sheets from foot pads of fsn/fsn mice stained for Ia+ Langerhans cells (LC) or Thy-1+ dendritic epidermal cells (Thy-1+ DEC) indicated a rise in LC numbers at the time of weaning, when the skin lesion becomes clinically evident. To further investigate this observation, epidermal sheets were obtained from the ear, dorsal skin, and foot pads from replicates of 6 female mice (both mutants and normal littermates) on weekly intervals from birth to 8 weeks of age. Dorsal skin epidermal thickness was quantitated by computer assisted image analysis and found to be significantly thickened from one week onward in the mutant mice. Using immunofluorescence microscopy, epidermal dendritic cell numbers were determined following staining with antibodies for the following markers: Ia, NLDC-145, and S-100 (for LC) or Thy 1.2 and asialo-GM1 (for Thy-1+ DEC). Use of all 5 markers to evaluate skin from 3 different locations yielded a subtle but significant increase in LC and Thy-1+ DEC in flaky skin mice. Of the three sites evaluated, the dorsal skin and ear epidermal sheets were most informative, which corresponded to the degree of pathological involvement. Mice doubly homozygous for fsn and for the severe combined immunodeficiency (scid) mutation developed the psoriasiform dermatitis. Bone marrow grafts from fsn/fsn homozygotes to homozygous scid/scid mice reproduce the skin lesion. These studies suggest that the psoriasiform dermatitis in the flaky skin mouse mutation is associated with abnormalities at the level of hematopoietic progenitor cells.

Role of Langerhans cells and other dendritic cells in viral diseases

Langerhans cells are part of a vast system of potent antigen-presenting cells known under the name of dendritic cells. During the last decade, much has been learned on dendritic cell involvement in the immune response to infectious diseases. This review briefly summarizes our current understanding of the role played by Langerhans cells and other dendritic cells in the pathogenesis of DNA and RNA virus infections. These data may form the basis for the development of innovative approaches in the diagnosis, prevention, and treatment of viral diseases.

Quantitative assessment of ATPase-positive epidermal dendritic (Langerhans) cells in piglets and adult swine

To assess the distribution pattern of Langerhans cells (LC) in normal porcine skin, epidermal sheets from six anatomical sites from three age-matched groups of male and female pigs were stained for ATPase activity. This histoenzymological technique is considered specific for Langerhans cells in normal epidermis. No statistically significant differences were observed between mean Langerhans cell density per mm2 of epidermis from male and female pigs, nor between different anatomical sites in the same age group. Statistically significant differences (P less than 0.0005) were observed when comparing group A one- to two-week-old piglets (463 to 518 LC mm-2) with group B six month olds (641 to 804 LC mm-2) and group C two years and over sows (741 to 830 LC mm-2). Morphological variations in the skin of young piglets, much thinner and with rudimentary or no epidermal rete pegs, could account for this significant variation.