Distribution of Ia antigen positive cells in chicken embryos infected with oncogenic Marek's disease virus (MDV) and MD vaccine viruses of serotypes 1, 2 and 3

Avian dendritic cells: Phenotype and ontogeny in lymphoid organs

Dendritic cells (DC) are critically important accessory cells in the innate and adaptive immune systems. Avian DCs were originally identified in primary and secondary lymphoid organs by their typical morphology, displaying long cell processes with cytoplasmic granules. Several subtypes are known. Bursal secretory dendritic cells (BSDC) are elongated cells which express vimentin intermediate filaments, MHC II molecules, macrophage colony-stimulating factor 1 receptor (CSF1R), and produce 74.3+ secretory granules. Avian follicular dendritic cells (FDC) highly resemble BSDC, express the CD83, 74.3 and CSF1R molecules, and present antigen in germinal centers. Thymic dendritic cells (TDC), which express 74.3 and CD83, are concentrated in thymic medulla while interdigitating DC are found in T cell-rich areas of secondary lymphoid organs. Avian Langerhans cells are a specialized 74.3-/MHC II+ cell population found in stratified squamous epithelium and are capable of differentiating into 74.3+ migratory DCs. During organogenesis hematopoietic precursors of DC colonize the developing lymphoid organ primordia prior to immigration of lymphoid precursor cells. This review summarizes our current understanding of the ontogeny, cytoarchitecture, and immunophenotype of avian DC, and offers an antibody panel for the in vitro and in vivo identification of these heterogeneous cell types.

Marek's disease virus may interfere with T cell immunity by TLR3 signals

Marek's disease virus (MDV) is a highly oncogenic alpha-herpesvirus that causes T cell immune suppression and malignant lymphomas in chickens. Toll-like receptor (TLR) plays a dominant role in antiviral T cell immunity. However, it is unclear whether MDV induced T cell immunity is associated with TLR-mediated immunity. In this study, the expression of 28 host genes that are involved in TLR-mediated immunity and MHC-medicated T cell immunity was evaluated in chicken thymus at 7, 14, 21 and 28 days post-infection (dpi). Our results demonstrated that 24 host immune-related genes were upregulated during MDV infection at 7 dpi; however, the expression of most of these genes decreased at 21 and 28 dpi. Notably, a positive correlation was found between the down-regulation of CD4, CD8 and TLR3 signals but not the MyD88-dependent TLR pathway. The present study expanded our knowledge of host immune responses against MDV infection and our results might provide a clue that MDV may interfere with T cell immune response through TLR3 signals.

Characterization of leukocyte subtypes in chicken inner ear sensory epithelia

Human hearing and balance require intact inner ear sensory hair cells, which transduce mechanical stimuli into electrical signals that are transmitted to the brain. Loss of hair cells after birth in mammals is irreversible, whereas birds are able to regenerate hair cells after insult and demonstrate ongoing hair cell production in the vestibular epithelia. Leukocytes reside in undamaged sensory epithelia of the avian inner ear and increase in number after trauma, prior to the proliferation of hair cell progenitors. It has been hypothesized that leukocyte-produced growth factors or cytokines may be involved in triggering hair cell regeneration. Little is known about the specific leukocyte subtypes present in avian ear. Immunohistochemistry with a panel of monoclonal antibodies to chicken leukocytes was used to identify leukocyte subtypes in normal posthatch chicken ear sensory epithelia. The responsiveness of the leukocytes to aminoglycoside-induced damage was also observed. Based on immunocytochemical and morphological criteria, we quantified leukocyte subtypes in normal and drug-damaged auditory and vestibular sensory epithelia. Data indicate that lymphocytes (B and T cells) do not reside in normal or drug-damaged ear sensory epithelia at 1-3 days post insult but are present in adjacent nonsensory tissues. The most common leukocytes in inner ear sensory epithelia are ramified cells of the myeloid lineage. Many of these are MHC class II positive, and a small percentage are mature tissue macrophages. An absence of leukocytes in lesioned areas of the auditory sensory epithelium suggests they may not play a critical role in triggering hair cell regeneration.

Immunological and regulatory functions of uninfected and virus infected immature and mature subtypes of dendritic cells--a review

In 1868, dendritic cells (DCs) were discovered in human skin by Paul Langerhans using gold staining. These cells were named Langerhans cells (LCs) after their discoverer who, due to their dendrites, regarded them as neurons. One hundred and eleven years were to pass until it was discovered that in vertebrates these cells originate in the bone marrow as monocytes. In the 1980s, DC research was mostly carried out on DCs that are present in different tissues of mice and humans. These studies revealed that after interaction with foreign antigens, skin LCs/DCs migrate through the lymph vessels to the draining lymph nodes and induce the two arms of the immune response. The isolation of DCs from tissue cell suspensions opened the way to studies on the cells' surface proteins and their ability to stimulate immune responses. During the 1990s, studies revealed the role of DCs in the activation of naive T cells in the lymph nodes and the regulatory properties of DCs in lymph nodes, thymus, gut, and spleen. Part A of the review deals with the DC system of human and mice and immunological and regulatory functions of subsets of DCs in the skin with reference to migrating and stationary DCs, as well as the connection between DCs and the nervous system. Furthermore, the origin of both follicular DCs that are present in lymphoid tissues and thymic DCs are discussed. Part B is devoted to virus infections of DCs with an emphasis on infections caused by human herpes viruses. Part C presents the modulation of DC gene expression in response to the influenza virus. Contemporary research focuses on the role of DCs in the immune systems of vertebrates. Moreover, studies are being conducted on the regulatory functions of DCs by tissue cells in different organs of vertebrates.