Demonstrating Agreement between Radio and Fluorescence Measurements of the Depth of Maximum of Extensive Air Showers at the Pierre Auger Observatory

We show, for the first time, radio measurements of the depth of shower maximum (X_{max}) of air showers induced by cosmic rays that are compared to measurements of the established fluorescence method at the same location. Using measurements at the Pierre Auger Observatory we show full compatibility between our radio and the previously published fluorescence dataset, and between a subset of air showers observed simultaneously with both radio and fluorescence techniques, a measurement setup unique to the Pierre Auger Observatory. Furthermore, we show radio X_{max} resolution as a function of energy and demonstrate the ability to make competitive high-resolution X_{max} measurements with even a sparse radio array. With this, we show that the radio technique is capable of cosmic-ray mass composition studies, both at Auger and at other experiments.

Transcriptomics of chicken cecal tonsils and intestine after infection with low pathogenic avian influenza virus H9N2

Influenza viruses cause severe respiratory infections in humans and birds, triggering global health concerns and economic burden. Influenza infection is a dynamic process involving complex biological host responses. The objective of this study was to illustrate global biological processes in ileum and cecal tonsils at early time points after chickens were infected with low pathogenic avian influenza virus (LPAIV) H9N2 through transcriptome analysis. Total RNA isolated from ileum and cecal tonsils of non-infected and infected layers at 12-, 24- and 72-h post-infection (hpi) was used for mRNA sequencing analyses to characterize differentially expressed genes and overrepresented pathways. Statistical analysis highlighted transcriptomic signatures significantly occurring 24 and 72 hpi, but not earlier at 12 hpi. Interferon (IFN)-inducible and IFN-stimulated gene (ISG) expression was increased, followed by continued expression of various heat-shock proteins (HSP), including HSP60, HSP70, HSP90 and HSP110. Some upregulated genes involved in innate antiviral responses included DDX60, MX1, RSAD2 and CMPK2. The ISG15 antiviral mechanism pathway was highly enriched in ileum and cecal tonsils at 24 hpi. Overall, most affected pathways were related to interferon production and the heat-shock response. Research on these candidate genes and pathways is warranted to decipher underlying mechanisms of immunity against LPAIV in chickens.

Inherited human c-Rel deficiency disrupts myeloid and lymphoid immunity to multiple infectious agents

We studied a child with severe viral, bacterial, fungal, and parasitic diseases, who was homozygous for a loss-of-function mutation of REL, encoding c-Rel, which is selectively expressed in lymphoid and myeloid cells. The patient had low frequencies of NK, effector memory cells reexpressing CD45RA (Temra) CD8+ T cells, memory CD4+ T cells, including Th1 and Th1*, Tregs, and memory B cells, whereas the counts and proportions of other leukocyte subsets were normal. Functional deficits of myeloid cells included the abolition of IL-12 and IL-23 production by conventional DC1s (cDC1s) and monocytes, but not cDC2s. c-Rel was also required for induction of CD86 expression on, and thus antigen-presenting cell function of, cDCs. Functional deficits of lymphoid cells included reduced IL-2 production by naive T cells, correlating with low proliferation and survival rates and poor production of Th1, Th2, and Th17 cytokines by memory CD4+ T cells. In naive CD4+ T cells, c-Rel is dispensable for early IL2 induction but contributes to later phases of IL2 expression. The patient's naive B cells displayed impaired MYC and BCL2L1 induction, compromising B cell survival and proliferation and preventing their differentiation into Ig-secreting plasmablasts. Inherited c-Rel deficiency disrupts the development and function of multiple myeloid and lymphoid cells, compromising innate and adaptive immunity to multiple infectious agents.

Response to Oxidative Burst-Induced Hypoxia Is Associated With Macrophage Inflammatory Profiles as Revealed by Cellular Genome-Wide Association

Background

In mammalian species, hypoxia is a prominent feature of inflammation. The role of hypoxia in regulating macrophage responses via alteration in metabolic pathways is well established. Recently, oxidative burst-induced hypoxia has been shown in murine macrophages after phagocytosis. Despite the available detailed information on the regulation of macrophage function at transcriptomic and epigenomic levels, the association of genetic polymorphism and macrophage function has been less explored. Previously, we have shown that host genetics controls approximately 80% of the variation in an oxidative burst as measured by nitric oxide (NO^-). Further studies revealed two clusters of transcription factors (hypoxia-related and inflammatory-related) are under the genetic control that shapes macrophages’ pro-inflammatory characteristics.

Material and Methods

In the current study, the association between 43,066 autosomal Single Nucleic Polymorphism (SNPs) and the ability of MDMs in production of NO^- in response to E. coli was evaluated in 58 Holstein cows. The positional candidate genes near significant SNPs were selected to perform functional analysis. In addition, the interaction between the positional candidate genes and differentially expressed genes from our previous study was investigated.

Results

Sixty SNPs on 22 chromosomes of the bovine genome were found to be significantly associated with NO^- production of macrophages. The functional genomic analysis showed a significant interaction between positional candidate genes and mitochondria-related differentially expressed genes from the previous study. Further examination showed 7 SNPs located in the vicinity of genes with roles in response to hypoxia, shaping approximately 73% of the observed individual variation in NO^- production by MDM. Regarding the normoxic condition of macrophage culture in this study, it was hypothesized that oxidative burst is responsible for causing hypoxia at the cellular level.

Conclusion

The results suggest that the genetic polymorphism via regulation of response to hypoxia is a candidate step that perhaps shapes macrophage functional characteristics in the pathway of phagocytosis leading to oxidative burst, hypoxia, cellular response to hypoxia and finally the pro-inflammatory responses. Since all cells in one individual carry the same alleles, the effect of genetic predisposition of sensitivity to hypoxia will likely be notable on the clinical outcome to a broad range of host-pathogen interactions.

Distinct miRNA Profile of Cellular and Extracellular Vesicles Released from Chicken Tracheal Cells Following Avian Influenza Virus Infection

Innate responses provide the first line of defense against viral infections, including the influenza virus at mucosal surfaces. Communication and interaction between different host cells at the early stage of viral infections determine the quality and magnitude of immune responses against the invading virus. The release of membrane-encapsulated extracellular vesicles (EVs), from host cells, is defined as a refined system of cell-to-cell communication. EVs contain a diverse array of biomolecules, including microRNAs (miRNAs). We hypothesized that the activation of the tracheal cells with different stimuli impacts the cellular and EV miRNA profiles. Chicken tracheal rings were stimulated with polyI:C and LPS from Escherichia coli 026:B6 or infected with low pathogenic avian influenza virus H4N6. Subsequently, miRNAs were isolated from chicken tracheal cells or from EVs released from chicken tracheal cells. Differentially expressed (DE) miRNAs were identified in treated groups when compared to the control group. Our results demonstrated that there were 67 up-regulated miRNAs, 157 down-regulated miRNAs across all cellular and EV samples. In the next step, several genes or pathways targeted by DE miRNAs were predicted. Overall, this study presented a global miRNA expression profile in chicken tracheas in response to avian influenza viruses (AIV) and toll-like receptor (TLR) ligands. The results presented predicted the possible roles of some DE miRNAs in the induction of antiviral responses. The DE candidate miRNAs, including miR-146a, miR-146b, miR-205a, miR-205b and miR-449, can be investigated further for functional validation studies and to be used as novel prophylactic and therapeutic targets in tailoring or enhancing antiviral responses against AIV.

The effect of host genetics on in vitro performance of bovine monocyte-derived macrophages

The dynamic interaction between the host and pathogens, along with environmental factors, influences the regulation of mammalian immune responses. Therefore, comprehensive in vivo immune-phenotyping during an active response to a pathogen can be complex and prone to confounding effects. Evaluating critical fundamental aspects of the immune system at a cellular level is an alternative approach to reduce this complexity. Therefore, the objective of the current study was to examine an in vitro model for functional phenotyping of bovine monocyte-derived macrophages (MDM), cells which play a crucial role at all phases of inflammation, as well influence downstream immune responses. As indicators of MDM function, phagocytosis and nitric oxide (NO^-) production were tested in MDM of 16 cows in response to 2 common bacterial pathogens of dairy cows, Escherichia coli and Staphylococcus aureus. Notable functional variations were observed among the individuals (coefficient of variation: 33% for phagocytosis and 70% in the production of NO^-). The rank correlation analysis revealed a significant, positive, and strong correlation (rho = 0.92) between NO^- production in response to E. coli and S. aureus, and a positive but moderate correlation (rho = 0.58) between phagocytosis of E. coli and S. aureus. To gain further insight into this trait, another 58 cows were evaluated solely for NO^- response against E. coli. The pedigree of the tested animals was added to the statistical model and the heritability was estimated to be 0.776. Overall, the finding of this study showed a strong effect of host genetics on the in vitro activities of MDM and the possibility of ranking Holstein cows based on the in vitro functional variation of MDM.

A genome-wide association study for natural antibodies measured in blood of Canadian Holstein cows

BACKGROUND

Natural antibodies (NAb) are an important component of the innate immune system, and fight infections as a part of the first line defence. NAb are poly-reactive and can respond non-specifically to antigens. Therefore, NAb may be a key trait when evaluating an animal's potential natural disease resistance. Variation in NAb is caused by both genetic and environmental factors. In this study genetic parameters of NAb were estimated and a genome-wide association study (GWAS) was performed to gain further understanding on the genes that are responsible for the observed genetic variation of NAb in Canadian Holsteins.

RESULTS

In total, blood samples of 1327 cows from 64 farms were studied. NAb binding to keyhole limpet hemocyanin (KLH) were determined via indirect ELISA. Immunoglobulin (Ig) isotypes, IgG and IgM, were evaluated. From the sample population, 925 cows were genotyped for 45,187 markers and each individual marker was tested to detect genetic variation in NAb levels. The relationships among animals was accounted for with genomic relationship. Results show heritabilities of 0.27 ± 0.064 (IgG) and 0.31 ± 0.065 (IgM). In total, 23 SNPs were found to be associated with IgG, but no SNPs were associated with IgM (FDR p-value < 0.05). The significant SNPs were located on autosomal chromosomes 1, 20 and 21 of the cow genome. Functional annotation analysis of the positional candidate genes revealed two sets of genes with biologically relevant functions related to NAb. In one set, seven genes with crucial roles in the production of antibody in B cells were associated with the trafficking of vesicles inside the cells between organelles. In the second set, two genes among positional candidate genes were associated with isotype class-switching and somatic hypermutation of B cells.

CONCLUSIONS

This study demonstrated the possibility of increasing NAb through selective breeding. In addition, the effects of two candidate pathways are proposed for further investigation of NAb production in Holsteins.

Development of the New Zealand White Rabbit Eye: I. Pre- and Postnatal Development of Eye Tunics

The New Zealand white (NZW) rabbit has been and is right now regularly utilized in ophthalmic surgery evaluation. Inside NZW rabbit eye, the visibility of ocular structures throughout surgical procedure is fantastic. Younger rabbits are used in different ages for the evaluation of ophthalmic surgery. Complete studies of ocular development in the NZW rabbits have not been reported previously. The aim of the present investigation was to describe the major landmarks and the time course of the pre- and post-natal development of the complete eye tunics of the NZW rabbit to give a superb model as well as a fruitful area for further ophthalmological investigations. Serial histological sections of NZW rabbit prenatal (E13-E28) and post-natal (P1-P14) stages were examined, respectively. The eye of the NZW rabbit developed in a similar manner to that of the human and domestic animals eyes; the principal differences were at the time of occurrence of certain developmental events, absence of pigmentation which represent an exploited benefit for ophthalmic surgery, remarkable Bowman's membrane at E25, poor developed ciliary stroma and juvenile retinal layer until P9. In human, the basic morphogenetic processes of the development of eye tunics are completed towards the end of the first half of gestation period. However, the latter represents the beginning stage of the development of eye tunics in the rabbit. Thus, allowing various extensive ophthalmic researches to be performed.

The effect of immunological status, in-vitro treatment and culture time on expression of eleven candidate reference genes in bovine blood mononuclear cells

Background

Technical feasibility of RNA quantification by real time RT-PCR has led to enormous utilization of this method. However, real time PCR results need to be normalized due to the high sensitivity of the method and also to eliminate technical variation. Normalization against a reference gene that is constitutively transcribed and has minimum variation among samples is the ideal method. Nevertheless, many studies have shown that there is no general reference gene(s) with ideal characteristics and candidate reference genes should be tested before being used as a “normalizer” in each study.

Methods

The current study investigated the effects of previous exposure of the host to experimental test antigens and culturing time on the expression of 11 candidate genes when blood mononuclear cells (BMCs) were cultured and treated in-vitro by hen egg white lysozyme, Candida albicans extract and a mitogen. Mononuclear cells were isolated and cultured from 12 bovine blood samples representing 3 different immunological statuses. The expression of candidate housekeeping genes were measured by real-time RT-PCR at 4 and 24 hours post culture. The expression of candidate genes were first compared between the two time points in untreated samples. Constitutively expressed genes were further tested in linear mixed effects models to examine the effect of previous host exposure and in-vitro treatments.

Results

Our findings showed that the expression of the most common reference genes, β-actin, and Glyceraldehydes-3-phosphate dehydrogenase (GAPDH), are significantly decreased at 24 hours after culturing BMCs, even without any treatment. The effect of culturing time was also significantly influenced the expression of 18s ribosomal RNA, β2-microglobulin, Tyrosine 3-monooxygenase/tryptophan 5-monoxygenase activation protein, zeta polypeptide (YWHAZ) in BMCs. Only the expression of C-terminal binding protein 1 (CTBP1) and RAD50 among all tested genes were consistent after treatment of cultured BMCs with C. albicans whole yeast extract and Hen Egg White Lysozyme (HEWL), respectively. In addition, expressions of CTBP1, and RAD50 were independent from previous exposure of the host to the antigen.

Conclusions

The results of this study demonstrated inconsistent expression of commonly used reference genes in untreated cultured BMCs over time. As this condition applies to negative controls in real time RT-PCR study designs, normalization against these genes can largely deceive the outcome, especially in kinetic studies. Moreover, the potential effects of immunological memory on the expression of reference genes should be considered if BMCs are collected from different individuals under different environmental conditions and if these cells are treated in-vitro by an antigen.

Genetic selection of cattle for improved immunity and health

The immune system is a sensing structure composed of tissues and molecules that are well integrated with the neuroendocrine system. This integrate system ensures non-self from self-discrimination. In this capacity the immune system provides detection and protection from a wide range of pathogens. In mammals, the immune system is regulated by several thousand genes (8-9% of the genome) which indicate its high genetic priority as a critical fitness trait providing survival of the species. Identifying and selectively breeding livestock with the inherent ability to make superior immune responses can reduce disease occurrence, improve milk quality and increase farm profitability. Healthier animals also may be expected to demonstrate improvements in other traits, including reproductive fitness. Using the University of Guelph's patented High Immune Response technology it is possible to classify animals as high, average, or low responders based on their genetic estimated breeding value for immune responsiveness. High responders have the inherent ability to produce more balanced and robust immune responses compared with average or low responders. High responders dairy cattle essentially have about one-half the disease occurrence of low responders, and can pass their superior immune response genes on to future generations thereby accumulating health benefits within the dairy herd.

The influence of genetic background versus commercial breeding programs on chicken immunocompetence

Immunocompetence of livestock plays an important role in farm profitability because it directly affects health maintenance. Genetics significantly influences the immune system, and the genotypic structure of modern fast-growing chickens has been changed, particularly after decades of breeding for higher production. Therefore, this study was designed to help determine if intensive breeding programs have adversely affected immunocompetence or whether the immune response profiles are controlled to greater extent by genetic background. Thus, 3 indigenous chicken populations from different genetic backgrounds and 2 globally available modern broiler strains, Ross 308 and Cobb 500, were evaluated for various aspects of immune response. These included antibody responses against sheep red blood cells and Brucella abortus antigen, as well as some aspects of cell-mediated immunocompetence by toe web swelling test and in vitro blood mononuclear cell proliferation. Significant differences (P < 0.05) in antibody responses to both antigens and cellular proliferation were observed among populations but not consistently between modern commercial strains versus the indigenous populations. In fact, the immune response profiles of Cobb 500 were similar to the indigenous populations, but varied compared with the other commercial strain. In addition, considerable variation was recorded between indigenous populations for all responses measured in this study. The results of this study suggest that the variation observed in immune responses between these strains of chickens is most likely due to differences in the genetic background between each strain of chicken rather than by commercial selection programs for high production.

Glanders outbreak at Tehran Zoo, Iran

BACKGROUND AND OBJECTIVES

In December 2010 four, lions and one tiger died at the Tehran zoo. Out of all samples, Burkholderia mallei (causative agent of Glanders) was isolated just from ulcer sample of the tiger which was imported to Iran from Russia.

MATERIALS AND METHODS

One nasal swab from a tiger and fifteen blood samples with anticoagulant belonging to one tiger and fourteen lions (four dead lions and eleven live lions) were collected and were inoculated directly onto the selective media. The isolate was identified by morphological and biochemical and API BBL tests and PCR using specific primers (Bma- IS407-flip). The standard (Razi Type Culture Collection RTCC: 2375) and tiger isolates were inoculated into 2 guinea pigs. All residue solipeds and carnivores were checked by Malleination test and Complement Fixation (CF) Test respectively.

RESULTS

One isolate of B. mallei was isolated from tiger's nasal swab. Both of B.mallei strains were recovered from inoculated animals. All of solipeds were negative by malleination test, however, 11 lions including 4 dead and 7 live lions out of 14 lions were positive in CF test for Glanders and all were put down by the authorities.

CONCLUSION

Active surveillance of Glanders is essential for solipeds, especially it's more important while being used to feed valuable carnivores like lions and tigers. Therefore, a reliable test like malleination must be carried out twice (first before transferring and one month after quarantine). Both test results should be negative for use for feeding.

Screening for cervical carcinoma using visual inspection with acetic acid

OBJECTIVE

To assess the performance of visual inspection with acetic acid (VIA) as a screening test for early detection of cervical carcinoma in the Dakahlia Governorate in Egypt.

METHODS

Diluted acetic acid (5%) was applied to the cervix during routine gynecologic examination. Women with positive results were referred for colposcopy. Those with negative results were referred for colposcopy only when they had clinical indications.

RESULTS

Among the 5,000 women who were screened using VIA, 409 were referred for colposcopy. Cervical intraepithelial neoplasia (CIN) was diagnosed in 151 (60%) of the 253 women with positive screening results and in 4 of the 156 women with negative screening results. There were 39 women with high-grade and 116 with low-grade CIN. The sensitivity and negative predictive value of the VIA screening test was 97%. Its positive predictive value was 60% for all grades of CIN and 90% for high-grade CIN.

CONCLUSION

Visual inspection with acetic acid, although associated with a relatively high rate of false-positive results, is a valuable test for the screening of cervical carcinoma.

Abnormal zinc and copper metabolism in hepatic steatosis

Abnormal Zinc and Copper metabolism were studied in rats with tetracycline-induced fatty liver and compared with normal rats. The present work recorded decreased serum zinc concentration with increased copper concentration in the tetracycline-injected rats. The results also showed that the liver and heart zinc were significantly decreased; meanwhile it was observed that the concentration of zinc in the kidney tissue of fatty liver rats was significantly raised in comparison with those of normal rats. Histopathological studies of the kidney tissue showed degenerative changes in the tables with areas of focal necrosis. Renal tubular necrosis in such cases is largely caused by the toxic degradation products of tetracycline metabolism. The kidney lesion together with impaired gastrointestinal absorption contributed to the hypozincaemia observed in the present results. Although the present data showed a significant reduction in serum zinc and significant rise in plasma insulin in the fatty liver rats there was nonsignificant correlation between the two variables as compared with the normal rats. The positive correlation between serum zinc concentration and reduced high-density lipoprotein cholesterol (HDL-C) emphasizes the role of zinc deficiency in atherosclerotic disease in fatty liver.

Effect of ultraviolet radiation on Ia expression by keratinocytes

Many skin diseases, such as graft-versus-host disease (GVHD), are marked by lymphocyte infiltrates in the skin. Severity of these diseases is often correlated with the induced expression of class II antigens (human, HLA-DR,; murine, Ia) by the keratinocytes. This suggests that HLA-DR-expressing keratinocytes may be involved in the pathogenesis of these diseases. Since some of these diseases are effectively treated with ultraviolet radiation (UVR), this study was conducted to determine whether UVR alters the keratinocyte expression of class II antigens. To test this hypothesis, 2 models of experimentally induced keratinocyte Ia expression were employed. First, athymic nude mice with one ear protected by electrical tape were exposed to UVR (450 J/m2/day on 4 consecutive days). They were then given an i.v. injection of normal mouse serum (NMS) to induce keratinocyte Ia expression. Keratinocytes in the UVR-exposed skin of these animals were not induced to express Ia; however, Ia-expressing keratinocytes were observed in the epidermis of shielded skin sites. Likewise, it was determined that UVR was capable of downregulating keratinocyte expression of Ia when administered to nude mice 7 d after receiving an injection of NMS. Second, employing a clinically relevant model, we found that Ia expression by keratinocytes in mice undergoing experimentally induced GVHD was abrogated by UVR treatment. This appeared to be a direct effect of the UVR, since keratinocytes in shielded skin sites and mucosal cells in the intestinal epithelium of animals with GVHD were shown to express Ia. These data provide compelling evidence for our hypothesis that decreased HLA-DR expression by keratinocytes in diseased skin treated with UVR is a mechanism by which UVR exerts its therapeutic effect.

An animal model of antibody binding in cutaneous lupus

To study antibody binding in cutaneous lupus, we used human skin grafted onto nude mice. By immunofluorescence examination, mice injected with anti-Ro (SS-A) sera from subacute cutaneous or neonatal lupus erythematosus patients showed evidence of human IgG deposited in the skin, while mice injected with anti-native DNA or normal sera did not. We present evidence that there is specific binding of anti-Ro (SS-A) antibodies to Ro (SS-A) antigen in the skin, and we propose that these antibodies may be directly involved in cutaneous disease.

Biology of Langerhans cells: analysis by experiments to deplete Langerhans cells from human skin

In vivo studies have demonstrated that various treatments of skin, e.g., UV irradiation, topical corticosteroids, and tape-stripping, will temporarily deplete the epidermis of Langerhans cells (LC). Whether this loss represents simply a loss of cell surface markers unique to LC, or actual depletion of cells, is unknown. By design, normal human skin transplanted to the congenitally athymic (nude) mouse is a system devoid of circulating precursors for human LC. Because LC have been shown to be of bone marrow origin, any depletion of these cells in this system should be permanent. Treatments to deplete LC from human skin grafts on nude mice after grafting included: (a) large doses of UV radiation (400 mJ/cm2 every 48 h, X 3), (b) potent high-dose topical corticosteroids (2.5 mg betamethasone valerate/cm2 every day, X 5), (c) tape-stripping (X 20). Treatments before grafting included: (a) treating donor skin with 900 R of gamma irradiation, (b) complement fixing monoclonal antibody to Ia-like antigens of LC, followed by fresh complement, (c) monoclonal antibody conjugated to toxins. Quantitation of the number of LC was analyzed on control and treated epidermal sheets using immunodiagnostic reagents, anti-HLA-DR, and surface ectoenzymes , ATPase. Results show that both UV irradiation and topical corticosteroids reduce the number of LC by these analyses. However, within 3 weeks, recovery to pretreatment levels has occurred. X-irradiation and tape-stripping were without effect. Despite evidence that the monoclonal antibody, complement, and toxic systems were delivered to the LC within the epidermis, there is no evidence that these treatments resulted in a decrease in LC. It appears that LC are currently either long-lived or replaced locally from a proliferative pool and that certain cell membrane determinants of human LC are somewhat differentially sensitive to UV radiation and corticosteroids.

Expression of Ia antigen on epidermal keratinocytes after the grafting of normal skin to nude mice

During the course of experimentation designed to evaluate the migration of host Langerhans cells (LC) into normal skin grafted onto nude mice, we observed that the epidermal cells of these grafts were induced to express la determinants solely of graft origin. The data presented herein indicate that the expression of la by normal epidermal cells correlates with the infiltration of host LC into the graft. This la expression is restricted to the keratinocytes within the epidermis of the grafted skin, is first observed 7 to 9 days post-grafting, and persists within the grafted skin for greater than 12 wk. The induction of la expression by keratinocytes appears to be the result of the environment that is provided by the nude mouse host and is independent of both passenger lymphocytes within the skin graft and allogeneic differences between graft and host. We strongly believe that these studies provide the basis for the development of an experimental animal model system for investigating the potential role that la expression by epidermal cells may play in enhancing the immune response to antigens encountered in the skin.

Expression of Ia antigen on epidermal keratinocytes after the grafting of normal skin to nude mice

During the course of experimentation designed to evaluate the migration of host Langerhans cells (LC) into normal skin grafted onto nude mice, we observed that the epidermal cells of these grafts were induced to express la determinants solely of graft origin. The data presented herein indicate that the expression of la by normal epidermal cells correlates with the infiltration of host LC into the graft. This la expression is restricted to the keratinocytes within the epidermis of the grafted skin, is first observed 7 to 9 days post-grafting, and persists within the grafted skin for greater than 12 wk. The induction of la expression by keratinocytes appears to be the result of the environment that is provided by the nude mouse host and is independent of both passenger lymphocytes within the skin graft and allogeneic differences between graft and host. We strongly believe that these studies provide the basis for the development of an experimental animal model system for investigating the potential role that la expression by epidermal cells may play in enhancing the immune response to antigens encountered in the skin.

Biology of Langerhans cells: selective migration of Langerhans cells into allogeneic and xenogeneic grafts on nude mice

A major question challenging immunobiologists relates to those mechanisms that control the selective movement of cells involved in immune and inflammatory processes at various tissue sites such as the skin. Little is known about those influences that control the selective migration of macrophage-like Langerhans cells (LC) to normal epidermis, where it is uniformly distributed. Mechanistically, this includes the interaction of blood-borne LC precursors with the vascular endothelium of the skin and those factors that control the migration of the LC into the avascular epidermal component of the skin. By using (i) monoclonal antibodies specific for I-region associated Ia antigens found on LC from various inbred strains of animals and (ii) the congenitally athymic (nude) mouse as an immunologically compromised recipient of allografts and selected xenografts, we developed a model system to study the factors that restrict LC migration into the epidermis. Using this model, which excludes the need to lethally x-irradiate graft recipients, we established that: (i) the ingress of LC does not show major histocompatibility complex restriction [LC of the nude host are capable of migrating into the epidermis of allogeneic and certain xenogeneic (rat) skin grafts]; (ii) host LC are incapable of migrating into the epidermis of guinea pig or human skin grafts; (iii) the ingress of host LC into the epidermis of the graft is not accompanied by an overgrowth of the graft by host epidermis; and (iv) LC or LC precursors are capable of dividing in the skin or, alternatively, represent an extremely long-lived cell population. The specificity of this model system provides a powerful tool to help understand many aspects of LC biology. Grafting human skin to the nude mouse not only provides a biologic support system for the graft but also is, by design, a system that is devoid of contaminating circulating precursor cell types. Manipulation of the experimental conditions is quite easy and provides a highly specific means to investigate many parameters of LC function.

Cell-mediated hyperacute rejection. I. Acute, accelerated, and hyperacute reactions

The morphology of first-set rejection of allogeneic murine skin grafts differs strikingly from that usually seen subsequent to sensitization. In the former, graft epithelium appears to be the primary target; in the latter, the endothelium of graft vessels. This difference suggests that different subsets of effector T cells may be involved. This paper reports an attempt to isolate, for further characterization, a T cell population associated with first-set rejection. The relationships between acute and hyperacute rejection of organ transplants and of murine skin grafts are discussed, as is the possible role of endothelium-specific antigens and receptors sites.