Quantitative analysis of CD1a (T6) positive Langerhans cells in human tonsil epithelium

Modulation of dendritic cell and T cell cross-talk during aging: The potential role of checkpoint inhibitory molecules

Dendritic cells (DCs) undergo continuous changes throughout life, and there is evidence that elderly DCs have a reduced capacity to stimulate T cells, which may contribute to impaired anti-tumour immune responses in elderly people with cancer. Changes in checkpoint inhibitory molecules/pathways during aging may be one mechanism that impairs the ability of elderly DCs to activate T cells. However, little is currently known regarding the combined effects of aging and cancer on DC and T cell inhibitory molecules/pathways. In this review, we discuss our current understanding of the influence of aging and cancer on key DC and T cell inhibitory molecules/pathways, the potential underlying cellular and molecular mechanisms contributing to their modulation, and the possibility of therapeutically targeting inhibitory molecules in elderly cancer patients.

Filaggrin inhibits generation of CD1a neolipid antigens by house dust mite-derived phospholipase

Atopic dermatitis is a common pruritic skin disease in which barrier dysfunction and cutaneous inflammation contribute to pathogenesis. Mechanisms underlying the associated inflammation are not fully understood, and although Langerhans cells expressing the nonclassical major histocompatibility complex (MHC) family member CD1a are known to be enriched within lesions, their role in clinical disease pathogenesis has not been studied. We observed that house dust mite (HDM) allergen generates neolipid antigens presented by CD1a to T cells in the blood and skin lesions of affected individuals. HDM-responsive CD1a-reactive T cells increased in frequency after birth in individuals with atopic dermatitis and showed rapid effector function, consistent with antigen-driven maturation. In HDM-challenged human skin, we observed phospholipase A2 (PLA2) activity in vivo. CD1a-reactive T cell activation was dependent on HDM-derived PLA2, and such cells infiltrated the skin after allergen challenge. Moreover, we observed that the skin barrier protein filaggrin, insufficiency of which is associated with atopic skin disease, inhibited PLA2 activity and decreased CD1a-reactive PLA2-generated neolipid-specific T cell activity from skin and blood. The most widely used classification schemes of hypersensitivity suggest that nonpeptide stimulants of T cells act as haptens that modify peptides or proteins; however, our results show that HDM proteins may also generate neolipid antigens that directly activate T cells. These data define PLA2 inhibition as a function of filaggrin, supporting PLA2 inhibition as a therapeutic approach.

Langerhans cells in the human tympanic membrane in health and disease: a morphometric analysis

HYPOTHESIS

The normal tympanic membrane contains Langerhans dendritic cells, and they play a role in the pathogenesis of chronic suppurative otitis media.

BACKGROUND

The presence of Langerhans dendritic cells in the normal tympanic membrane is disputed. However, they have been identified in tympanic membranes of patients with otitis media. A quantitative analysis of the distribution and morphology of these cells in the types of chronic suppurative otitis media has not been undertaken.

METHODS

Samples of normal cadaveric tympanic membranes and those from patients with chronic suppurative otitis media of the tubotympanic and atticoantral varieties were stained with the immunohistochemical marker CD1a. The number of cells per unit length of basement membrane, diameters of cells, and number and length of dendritic processes were compared between the groups.

RESULTS

CD1a-positive Langerhans dendritic cells were present in the normal tympanic membrane. The number of cells per unit length of basement membrane, diameters of cells, and the length of dendritic processes increased significantly in tubotympanic disease and in atticoantral disease, the difference being more pronounced in the latter form of otitis media.

CONCLUSION

Langerhans cells are present in the normal tympanic membrane, and they probably play differing roles in the pathogenesis of tubotympanic and atticoantral forms of chronic suppurative otitis media.

A review of the pathogenesis of adult peritonsillar abscess: time for a re-evaluation

OBJECTIVES

To perform a multifactorial exploration of the aetiology of peritonsillar abscess (PTA) in adults, in order to develop greater clinical understanding of the condition and improve management.

DESIGN

A literature review exploring key pathogens, predisposing host factors and current pathogenic hypotheses.

METHODS

A PubMed search for articles published between January 1980 and January 2012 using the terms 'peritonsillar abscess AND microbiology', 'peritonsillar abscess AND pathophysiology' and 'peritonsillar abscess AND etiology'.

RESULTS

Major pathogens in PTA are opportunistic microflora. Group A streptococcal PTA infections present differently from polymicrobial PTA. A number of host factors influence the conditions required for the pathogenesis of PTA.

CONCLUSIONS

PTA is clinically distinct from acute tonsillitis and occurs in people with a chronic underlying susceptibility. Targeting host factors, including oral hygiene, antibiotic use and smoking, may prevent PTA. Re-education of clinicians concerning the aetiology of PTA is necessary for appropriate disease management.

Evidence for a stepwise program of extrathymic T cell development within the human tonsil

The development of a broad repertoire of T cells, which is essential for effective immune function, occurs in the thymus. Although some data suggest that T cell development can occur extrathymically, many researchers remain skeptical that extrathymic T cell development has an important role in generating the T cell repertoire in healthy individuals. However, it may be important in the setting of poor thymic function or congenital deficit and in the context of autoimmunity, cancer, or regenerative medicine. Here, we report evidence that a stepwise program of T cell development occurs within the human tonsil. We identified 5 tonsillar T cell developmental intermediates: (a) CD34⁺CD38dimLin⁻ cells, which resemble multipotent progenitors in the bone marrow and thymus; (b) more mature CD34⁺CD38brightLin⁻ cells; (c) CD34⁺CD1a⁺CD11c⁻ cells, which resemble committed T cell lineage precursors in the thymus; (d) CD34⁻CD1a⁺CD3⁻CD11c⁻ cells, which resemble CD4⁺CD8⁺ double-positive T cells in the thymus; and (e) CD34⁻CD1a⁺CD3⁺CD11c⁻ cells. The phenotype of each subset closely resembled that of its thymic counterpart. The last 4 populations expressed RAG1 and PTCRA, genes required for TCR rearrangement, and all 5 subsets were capable of ex vivo T cell differentiation. TdT⁺ cells found within the tonsillar fibrous scaffold expressed CD34 and/or CD1a, indicating that this distinct anatomic region contributes to pre-T cell development, as does the subcapsular region of the thymus. Thus, we provide evidence of a role for the human tonsil in a comprehensive program of extrathymic T cell development.

Depletion of Langerhans cells in the tongue from patients with advanced-stage acquired immune deficiency syndrome: relation to opportunistic infections

AIMS

To quantify and compare the expression of Langerhans cells (LCs) in the tongue mucosa of AIDS patients with different opportunistic infections, and from acquired immune deficiency syndrome (AIDS) and non-AIDS patients with normal tongues, using autopsy material.

METHODS AND RESULTS

Human leucocyte antigen D-related (HLA-DR), CD1a and CD83 antibodies were used to identify and quantify LCs by immunohistochemistry in tongue tissue of 40 AIDS patients (10 with lingual candidiasis, 10 with lingual herpes, 10 with oral hairy leukoplakia and 10 with no lesions) and 23 tongues from human immunodeficiency virus (HIV)-negative control patients. Quantification was performed by means of conventional morphometry in four different regions (anterior, middle, posterior and lateral) of the tongue. The results were expressed as positive cells per area of epithelium. The AIDS patients presented a lower density of CD1a(+) cells (P < 0.001), HLA-DR (P < 0.003) and CD83 (P < 0.001) in all regions of the tongue compared to the non-AIDS control group. However, no differences in any of the markers were found when AIDS patients with different opportunistic infections were compared with AIDS patients without tongue infection.

CONCLUSIONS

Advanced stage AIDS patients showed a depletion of LCs in the tongue mucosa. HIV infection induces cytopathic changes in LCs, contributing to their depletion regardless of the presence of oral infections.

CD1a expression defines an interleukin-12 producing population of human dendritic cells

Human and murine dendritic cell (DC) subsets are often defined by phenotypic features that predict their functional characteristics. In humans and mice, DC have been shown to have the ability to polarize naive CD4 T cells to a T helper type 1 (Th1) or Th2 phenotype. However, human myeloid DC generated from monocytes (monocyte-derived DC) have often been regarded as a homogeneous population, both phenotypically and functionally. Monocytes give rise to subpopulations of DC in vitro that can be separated on the basis of their expression of CD1a, a well-described DC subset marker. Importantly, we show that the CD1a(+) DC subset produces significant quantities of interleukin-12p70 (IL-12p70) upon stimulation and, similar to the murine CD8 alpha(+) DC subset, can polarize naive CD4(+) T cells to a Th1 phenotype. In contrast, CD1a(-) DC, similar to murine CD8 alpha(-) DC, do not produce significant amounts of IL-12p70 upon stimulation or polarize T cells to a Th1 phenotype. Like monocyte-derived DC, CD1a(+) and CD1a(-) DC subsets obtained from CD34(+) haematopoietic progenitors under distinct culture conditions were found to have these same features, suggesting that CD1a expression is a marker for myeloid DC that are a major source of IL-12 and Th1 CD4(+) T cell polarization in man.

Evaluation of Langerhans' cells in normal and eczematous dermatitis skin by CD1a protein immunohistochemistry: preliminary findings

BACKGROUND

Langerhans' cells (CD1a positive, bone marrow-derived cells), are the antigen presenting cells of the skin. Our knowledge about the status of these cells in eczematous dermatitis is incomplete.

AIM

This study tests the hypothesis that 'the development of eczematous dermatitis is associated with alterations of Langerhans' cells'.

MATERIALS AND METHODS

Biopsy specimens from patients with eczematous dermatitis and normal skin (20 cases, each) were studied. Langerhans' cells were stained for CD1a using imunoperoxidase-staining methods and mouse monoclonal antibodies.

RESULTS

In normal skin, CD1a+ Langerhans' cells were seen in suprabasal position. In eczematous dermatitis skin, CD1a positive cells were seen scattered in the acanthotic epidermis. Compared with normal skin, the mean values of the Langerhans' cells were statistically significantly higher in eczematous dermatitis [epidermal Langerhans' cells: 1.20 (standard error of mean, SEM, 0.13) vs. 2.50 (SEM, 0.16); and dermal Langerhans' cells: 1.30 (SEM, 0.15) vs. 2.7 (SEM, 0.15); for normal and eczematous skin, respectively; p < 0.05].

CONCLUSIONS

The higher Langerhans' cell counts in eczematous dermatitis suggest a possible link between antigen presenting capabilities of these cells, and development of these lesions.

Biology of dendritic cells in aging

Dendritic cells are central to the generation of both immunity and tolerance. This review focuses on the alterations in the functions of dendritic cells in aged and its consequences on both tolerance and immunity. We have discussed certain mechanisms responsible for the defective dendritic cell function associated with aging.

Aging and the dendritic cell system: implications for cancer

The immune system shows a decline in responsiveness to antigens both with aging, as well as in the presence of tumors. The malfunction of the immune system with age can be attributed to developmental and functional alterations in several cell populations. Previous studies have shown defects in humoral responses and abnormalities in T cell function in aged individuals, but have not distinguished between abnormalities in antigen presentation and intrinsic T cell or B cell defects in aged individuals. Dendritic cells (DC) play a pivotal role in regulating immune responses by presenting antigens to naïve T lymphocytes, modulating Th1/Th2/Th3/Treg balance, producing numerous regulatory cytokines and chemokines, and modifying survival of immune effectors. DC are receiving increased attention due to their involvement in the immunobiology of tolerance and autoimmunity, as well as their potential role as biological adjuvants in tumor vaccines. Recent advances in the molecular and cell biology of different DC populations allow for addressing the issue of DC and aging both in rodents and humans. Since DC play a crucial role in initiating and regulating immune responses, it is reasonable to hypothesize that they are directly involved in altered antitumor immunity in aging. However, the results of studies focusing on DC in the elderly are conflicting. The present review summarizes the available human and experimental animal data on quantitative and qualitative alterations of DC in aging and discusses the potential role of the DC system in the increased incidence of cancer in the elderly.

Deterioration of the Langerhans cell network of the human gingival epithelium with aging

Dendritic cells (DCs) are the professional antigen-presenting cells responsible for initiating of the immune response. Langerhans cells (LCs) are a type of DC that is a permanent resident of the oral epithelium. LCs are organized conforming a network in such a way as to maximize their surface area for efficient apprehension of antigens. To detect age-related changes in the LCs network, fragments of gingival epithelium spontaneously accompanying dental removals were processed by immunohistochemistry. Monoclonal antibody CD1a followed by biotinized immunoglobulin-streptoavidin peroxidase were used to identify the LCs with the light microscope. LC density and LC types were analyzed according to their morphology and intraepithelial distribution. In the older age group (61-74 years) the density was significantly lower than in the younger age groups. Morphologically, LCs showed fewer dendritic-branching processes and had a rounded shape in the older age group. Present observations indicate that the LC network changes markedly with aging. These results suggest that immunological defense of the oral tissue might be compromised in old age.