Canine MHC-class II antigens on B and T lymphocytes

Reactivity of HLADR antibody manifests expression of surface MHC II molecules on peripheral blood T lymphocytes in new world monkeys

BACKGROUND

Major histocompatibility complex (MHC) class II molecules expressed on B cells, monocytes and dendritic cells present processed peptides to CD4+ T cells as one of the mechanisms to combat infection and inflammation.

AIM

To study MHC II expression in a variety of nonhuman primate species, including New World (NWM) squirrel monkeys (Saimiri boliviensis boliviensis), owl monkeys (Aotus nancymae), common marmosets (Callithrix spp.), and Old World (OWM) rhesus (Macaca mulatta), baboons (Papio anubis).

METHODS

Two clones of cross-reactive mouse anti-human HLADR monoclonal antibodies (mAb) binding were analyzed by flow cytometry to evaluate MHC II expression on NHP immune cells, including T lymphocytes in whole blood (WB) and peripheral blood mononuclear cells (PBMC).

RESULTS

MHC class II antibody reactivity is seen with CD20+ B cells, CD14+ monocytes and CD3+ T lymphocytes. Specific reactivity with both clones was demonstrated in T lymphocytes: this reactivity was not inhibited by purified CD16 antibody but was completely inhibited when pre-blocked with purified unconjugated MHC II antibody. Freshly prepared PBMC also showed reactivity with T lymphocytes without any stimulation. Interestingly, peripheral blood from rhesus macaques and olive baboons (OWM) showed no such T lymphocyte associated MHCII antibody reactivity.

DISCUSSION & CONCLUSION

Our results from antibody (MHC II) reactivity clearly show the potential existence of constitutively expressed (with no stimulation) MHC II molecules on T lymphocytes in new world monkeys. These results suggest that additional study is warranted to evaluate the functional and evolutionary significance of these finding and to better understand MHC II expression on T lymphocytes in new world monkeys.

The gene expression profile and cell of origin of canine peripheral T-cell lymphoma

BACKGROUND

Peripheral T-cell lymphoma (PTCL) refers to a heterogenous group of T-cell neoplasms with poor treatment responses and survival times. Canine PTCL clinically and immunophenotypically resembles the most common human subtype, PTCL-not otherwise specified (PTCL-NOS), leading to interest in this canine disease as a naturally occurring model for human PTCL. Gene expression profiling in human PTCL-NOS has helped characterize this ambiguous diagnosis into distinct subtypes, but similar gene expression profiling in canine PTCL is lacking.

METHODS

Bulk RNA-sequencing was performed on tumor samples from 33 dogs with either CD4+ (26/33), CD8+ (4/33), or CD4-CD8- (3/33) PTCL as diagnosed by flow cytometry, and sorted CD4+ and CD8+ lymphocytes from healthy control dogs. Following normalization of RNA-seq data, we performed differential gene expression and unsupervised clustering methods. Gene set enrichment analysis was performed to determine the enrichment of canine CD4+ PTCL for human PTCL-NOS, oncogenic pathways, and various stages of T-cell development gene signatures. We utilized gene set variation analysis to evaluate individual canine CD4+ PTCLs for various human and murine T-cell and thymocyte gene signatures. Cultured canine PTCL cells were treated with a pan-PI3K inhibitor, and cell survival and proliferation were compared to DMSO-treated controls. Expression of GATA3 and phosphorylated AKT was validated by immunohistochemistry.

RESULTS

While the canine CD4+ PTCL phenotype exhibited a consistent gene expression profile, the expression profiles of CD8+ and CD4-CD8- canine PTCLs were more heterogeneous. Canine CD4+ PTCL had increased expression of GATA3, upregulation of its target genes, enrichment for PI3K/AKT/mTOR signaling, and downregulation of PTEN, features consistent with the more aggressive GATA3-PTCL subtype of human PTCL-NOS. In vitro assays validated the reliance of canine CD4+ PTCL cells on PI3K/AKT/mTOR signaling for survival and proliferation. Canine CD4+ PTCL was enriched for thymic precursor gene signatures, exhibited increased expression of markers of immaturity (CD34, KIT, DNTT, and CCR9), and downregulated genes associated with the T-cell receptor, MHC class II associated genes (DLA-DQA1, DLA-DRA, HLA-DQB1, and HLA-DQB2), and CD25.

CONCLUSIONS

Canine CD4+ PTCL most closely resembled the GATA3-PTCL subtype of PTCL-NOS and may originate from an earlier stage of T-cell development than the more conventionally posited mature T-helper cell origin.

Comparative analysis of mRNA expression of surface antigens between histiocytic and nonhistiocytic sarcoma in dogs

Background

Definitive diagnosis of histiocytic sarcoma (HS) in dogs is relatively difficult by conventional histopathological examination because objective features of HS are not well defined.

Hypothesis

Quantitative analysis of mRNA expression of selected cellular surface antigens (SAs) specific to HS in dogs can facilitate objective and rapid diagnosis.

Animals

Dogs with HS (n = 30) and dogs without HS (n = 36), including those with other forms of lymphoma (n = 4), inflammatory diseases (n = 6), and other malignant neoplasias (n = 26).

Methods

Retrospective clinical observational study. Specimens were collected by excisional biopsy, needle core biopsy, or fine needle aspiration. To determine HS detection efficacy, mRNA expression levels of selected SAs specific to HS in dogs, including MHC class IIα, CD11b, CD11c, and CD86, were quantitatively analyzed using real‐time quantitative polymerase chain reaction.

Results

Each SA mRNA expression level was significantly higher in HS dogs than in non‐HS dogs (P = .0082). Cutoff values for discriminating between HS and non‐HS dogs based on these expression levels were calculated on the basis of receiver‐operating characteristic analysis. Accuracy of the cutoff values, including MHC class IIα, CD11b, CD11c, and CD86, was 87.9, 86.4, 86.4, and 84.8%, respectively.

Conclusions and Clinical Importance

Our results suggest that quantitative analysis of mRNA expression of the selected SAs could be an adjunctive diagnostic technique with high diagnostic accuracy for HS in dogs. Substantial investigation is required for exclusion of diseases with similar cell types of origin to lymphoma.

Immunisation with an allogeneic peptide promotes the induction of antigen-specific MHC II(pos) CD4+ rat T cells demonstrating immunostimulatory properties

BACKGROUND

The phenomenon of T cell stimulation by MHC class II expressing (MHC II(pos)) CD4+ T cells has been intensively investigated for T cell clones but, so far, not for native T cells. The extensive use of T cell clones may explain the inconsistent outcomes of T cell-mediated antigen-presentation. Therefore, we used freshly isolated primed rat CD4+ T cells induced by immunisation with an allogeneic peptide P1, which is involved in allograft rejection.

METHODS

MHC II(pos) and MHC II(neg) CD4+ T cells were isolated from popliteal lymph nodes of P1-immunised Lewis rats and were purified by combining depletion and positive selection steps. Purified MHC II(pos) CD4+ T cells and MHC II(neg) CD4+ T cells (10⁵ cells per well each) were autostimulated or restimulated with P1-loaded (33 μg/ml peptide P1) and subsequently irradiated (with 20 Gy) autologous DC.

RESULTS

Seven days after immunisation, a small population of MHC II(pos) CD4+ T cells was detectable (approximately 8.0% of total lymph node cells), as well as a large population of MHC II(neg) CD4+ T cells (up to 45%). Antigen-specific proliferation was observed for both T cell populations but only P1-loaded MHC II(pos) CD4+ T cells presented antigen presenting cell (APC) function for P1-primed T cells. Their inability to activate unprimed T cells may be due to impaired surface expression of costimulatory molecules (CD80 and CD86).

CONCLUSION

Immunisation with the allogeneic peptide antigen P1 induced antigen-specific MHC II(pos) CD4+ rat T cells demonstrating perfect APC function for primed T cells in vitro.

Joint Report of the Fifth International Workshop on Lymphocyte Alloantigens of the Horse, Baton Rouge, Louisiana, 31 October-1 November 1987

Six laboratories participated in the Fifth International Workshop on Lymphocyte Alloantigens of the Horse, testing 132 alloantisera against lymphocytes of 880 horses chosen to represent different families and breeds. Most of the alloantisera were produced by lymphocyte immunization between horses matched at the ELA-A locus. All horses were also tested with antisera contributed to the workshop by participating laboratories which identified ELA specificities A1-A10 and W12-W21. Previously identified workshop specificities ELA-W14, W15 and W19 were accepted as products of the ELA-A locus based on family and population studies by the workshop. Their designations were changed to ELA-A14, ELA-A15 and ELA-A19, respectively. Two new specificities were identified, namely ELA-W22 (W22) and ELA-W23 (W23). Population and family studies indicated that W22 and W23 as well as W13 are products of an ELA locus other than ELA-A. The presence of these specificities was correlated with the presence of certain ELA-A locus specificities, e.g. W13 with A3, W22 with A2 and W23 with A5. However, the association was not complete and W13, W22 and W23 also segregated with other ELA-A specificities in some families. Evidence for recombination was found between the ELA-A locus and the locus or loci encoding these specificities resulting in seven recombinant haplotypes found among the data presented in this workshop. Further studies are required for definitive assignment of the specificities to a class I or class II locus.

MHC class II expression by follicular keratinocytes in canine demodicosis—An immunohistochemical study

MHC class II proteins present fragments of extra cellular antigen to stimulate CD4(+) T lymphocytes. Aim of this study was the detection of MHC class II antigens on different cutaneous cells in canine demodicosis. Histopathological and immunohistochemical examination of skin biopsies from 44 dogs with demodicosis is reported. The control group consisted of skin biopsies taken from 10 necropsied dogs without obvious skin lesions. The immunohistological assessment of the MHC class II expression revealed MHC class II proteins on different cell types of infiltrating inflammatory cells, i.e. APCs (antigen-presenting cells), macrophages, T lymphocytes and B lymphocytes. The plasma cells, however, only showed expression in 32 (73%) of 44 cases. Generally it was noticeable that most plasma cells but never all of them expressed MHC class II. Neutrophils, mast cells and eosinophils were MHC class II negative. Furthermore, in 39 biopsies (89%) from dogs with demodicosis MHC class II positive follicular keratinocytes were found. The control group did not show MHC class II expression on epithelial cells. Concerning the endothelial cells, a total of 25 biopsies (57%) showed MHC class II expression in which different vascular plexuses were affected by staining. This examination shows that MHC class II expression in the skin of dogs suffering form demodicosis is elevated. Especially the MHC class II expression by follicular keratinocytes seems to be conspicuous. We hypothesize that this is in association with the development and the maintenance of follicular inflammation.

Role of MHC class II expressing CD4+ T cells in proteolipid protein(91-110)-induced EAE in HLA-DR3 transgenic mice

MHC class II molecules play a central role in the control of adaptive immune responses through selection of the CD4(+) T cell repertoire in the thymus and antigen presentation in the periphery. Inherited susceptibility to autoimmune disorders such as multiple sclerosis, rheumatoid arthritis and IDDM are associated with particular MHC class II alleles. Advent of HLA transgenic mice has helped us in deciphering the role of particular HLA DR and DQ class II molecules in human autoimmune diseases. In mice, the expression of class II is restricted to professional antigen-presenting cells (APC). However, in humans, class II is also expressed on T cells, unlike murine T cells. We have developed new humanized HLA class II transgenic mice expressing class II molecules not only on APC but also on a subset of CD4(+) T cells. The expression of class II on CD4(+) T cells is inducible, and class II(+) CD4(+) T cells can present antigen in the absence of APC. Further, using EAE, a well-established animal model of MS, we tested the functional significance of these class II(+) CD4(+) T cells. DR3.AEo transgenic mice were susceptible to proteolipid protein(91-110)-induced EAE and showed CNS pathology accompanied by widespread inflammation and demyelination seen in human MS patients, suggesting a role for class II(+) CD4(+) T cells in the pathogenesis.

Major histocompatibility class II expression in the normal canine cornea and in canine chronic superficial keratitis

OBJECTIVE

To compare the expression of major histocompatibility complex (MHC) class II antigen in the corneas of normal dogs and dogs affected with chronic superficial keratitis (CSK).

METHODS

MHC class II expression was determined in frozen sections of normal canine cornea and cornea from lesions of CSK by immunohistochemistry using a monoclonal antibody directed against the canine MHC class II molecule. Langerhans cell phenotype was determined morphologically and by histochemical determination of ATPase activity. To determine the influence of gamma interferon on expression of MHC class II molecules by corneal cells, corneal explants were cultured with the cytokine and MHC class II expression determined as above.

RESULTS

Numerous MHC class II-expressing cells were demonstrated within the stroma and epithelium of the normal corneal limbus and conjunctival epithelium while very little MHC class II expression was detected in the central region of normal canine cornea. In limbal and conjunctival epithelium, cells expressing MHC class II antigen showed ATPase activity, suggesting that they were Langerhans cells. Corneas from dogs with CSK showed MHC class II expression associated with stromal cells, some of which exhibited a dendritic morphology while most were lymphocytic. Corneal epithelial cells within the lesion also aberrantly expressed MHC class II. Corneal explants expressed MHC class II to varying degrees after differing periods of incubation with the cytokine gamma interferon.

CONCLUSIONS

While the normal central cornea has little MHC class II expression, aberrant expression occurs in CSK, associated with secretion of gamma interferon by infiltrating CD4-expressing lymphocytes. Although this change is likely to be a secondary feature of the CSK lesion, increased MHC class II expression may play a part in perpetuating the corneal inflammation seen in the disease.

Cellular immunophenotyping of exfoliative dermatitis in canine leishmaniosis (Leishmania infantum)

Lymphocyte subsets, major histocompatibility complex (MHC)-II expressing cells and number of amastigotes in the epidermis and dermis were investigated immunohistochemically in 48 dogs with patent leishmaniosis, with or without exfoliative dermatitis (ED) to study the immunopathogenesis of this common cutaneous form of the disease. Skin biopsies were obtained and compared for ED sites (group A, n = 26), normal-appearing skin from the same animals (group B, n = 24), and leishmanial dogs not exhibiting ED (group C, n = 22), and normal controls (group D, n = 22). The CD3+, CD45RA+, CD4+, CD8+ (CD8a+), CD21+, and MHC-II+ cells and leishmania amastigotes were identified immunohistochemically and counted with the aid of an image analysis system. Pyogranulomatous to granulomatous dermatitis, expressed in various histopathological patterns, was noticed in all groups A and B and in half of group C dogs. In the epidermis, the low number of T-cells and their subsets did not differ significantly between groups A and B, but CD8+ outnumbered CD4+ lymphocytes in both groups. MHC-II+ expression on epidermal keratinocytes was intense in the skin with and without lesions from dogs with ED but not in group C dogs. CD3+, CD8+ and MHC-II+ cells were fewer in group C compared to group A and B dogs. In the dermis, CD3+ cells in group A animals were mainly represented by the CD8+. CD45RA+ and CD21+ cells were also seen in high numbers. MHC-II expression, potentially in lymphocytes, fibroblasts, dendritic cells, and macrophages was intense. The numbers of all cellular subpopulations in the dermis were significantly different between the groups, being highest in group A and lowest in group D. In sebaceous adenitis sites, CD4+ outnumbered CD8+ cells in contrast to the neighbouring dermis and the epidermis. The number of CD21+ and CD45RA+ cells was much lower in the inflamed sebaceous glands compared to the dermis. Finally, the number of amastigotes in the normal-appearing skin was significantly higher in the ED dogs (group B) than in those not exhibiting this cutaneous form of the disease (group C).

Function and regulation of MHC class II molecules in T-lymphocytes: of mice and men

The main function of major histocompatibility complex (MHC) class II molecules is to present processed antigens, which are derived primarily from exogenous sources, to CD4(+) T-lymphocytes. MHC class II molecules thereby are critical for the initiation of the antigen-specific immune response. Besides antigen presentation, growing evidence is showing that ligation of MHC class II molecules also activates intracellular signaling pathways, frequently leading to apoptosis. Constitutive expression of MHC class II molecules is confined to professional antigen-presenting cells (APC) of the immune system, and in nonprofessional APCs MHC class II molecules can be induced by a variety of immune regulators. Interestingly, activated T cells from many species, with the exception of mice, synthesize and express MHC class II molecules at their cell surface. In this review, we discuss our current knowledge on the transcriptional regulation of MHC class II expression in activated human and mouse T cells, and the contribution of DNA methylation of the T-cell employed class II transactivator promoter III to the MHC class II deficiency of mouse T cells. We also discuss the proposed functions of the activated T cell synthesized and expressed MHC class II molecules, including antigen presentation, T-T cell interactions, and MHC class II-mediated intracellular signaling.

Extensive interbreed, but minimal intrabreed, variation of DLA class II alleles and haplotypes in dogs

The DLA class II genes in the dog major histocompatibility complex are highly polymorphic. To date, 52 DLA-DRB1, 16 DLA-DQA1 and 41 DLA-DQB1 allelic sequences have been assigned. The aim of this study was to examine the intrabreed and interbreed variation of DLA allele and haplotype frequencies in dogs, and to ascertain whether conserved DLA class II haplotypes occur within and between different breeds. One thousand and 25 DNA samples from over 80 different breeds were DLA class II genotyped, the number of dogs per breed ranging from 1 to 61. DNA sequence based typing and sequence specific oligonucleotide probing were used to characterize dogs for their DLA-DRB1, DQA1 and DQB1 alleles. The high frequency of DLA class II homozygous animals (35%), allowed the assignment of many haplotypes despite the absence of family data. Four new DLA alleles were identified during the course of this study. Analysis of the data revealed considerable interbreed variation, not only in allele frequency, but also in the numbers of alleles found per breed. There was also considerable variation in the number of breeds in which particular alleles were found. These interbreed variations were found in all three DLA class II loci tested, and also applied to the three-locus haplotypes identified. Within this data set, 58 different DLA-DRB1/DQA1/DQB1 three-locus haplotypes were identified, which were all found in at least two different animals. Some of the haplotypes appeared to be characteristic of certain breeds. The high interbreed, and relatively low intrabreed, variation of MHC alleles and haplotypes found in this study could provide an explanation for reports of interbreed variation of immune responses to vaccines, viruses and other infections.

A standardized gating technique for the generation of flow cytometry data for normal canine and normal feline blood lymphocytes

Flow cytometry is becoming a commonly used technique to characterize a variety of cells. It provides a powerful application to rapidly determine the relative percentages of T-lymphocyte subsets and B-lymphocytes. The effectiveness of its application, however, is dependent on standardization, especially in a clinical setting. Application of flow cytometry to veterinary diagnostics has been limited by the unavailability of reagents and by the unstandardized characterization of normal values using antibodies not commercially available, but typically provided through the generosity of other researchers. This paper presents a standardized gating protocol, and average values and ranges observed for normal canine and feline blood lymphocytes using commercially available antibodies to cell surface markers for CD5, CD3, CD4, CD8, MHC II, and B lymphocytes. The averages for these markers on gated lymphocytes were as follows: Canine CD5 83.3%, Canine CD4 45.0%, Canine CD8 28.8%, Canine MHC II 98.0%, Canine B Cell 12.9%, Canine CD4/CD8 ratio 1.87, Feline T lymphocytes 77.3%, Feline CD4 44.5%, Feline CD8 25.7%, Feline B Cell 24.1%, Feline CD4/CD8 Ratio 1.75. Normal values were also established for a mixed breed group of dogs, and old versus young dogs. This information will provide researchers and clinicians with a standardized protocol for gating, which establishes a basis for comparison between techniques, and a measure of phenotypic percentages for flow cytometry in normal dogs and cats based on this standardization and commercially available antibodies.

Recognition of major histocompatibility complex class II antigens by two anti-HLA-DR monoclonal antibodies on canine marrow cells correlates with effects on in vitro and in vivo hematopoiesis

BACKGROUND

The role of major histocompatibility complex class II antigens in hematopoiesis is not well defined. We have shown that in vitro depletion of HLA-DR+ cells from canine marrow (e.g., by anti-HLA-DR monoclonal antibody [mAb] H81.9 and complement) prevents hematopoietic recovery. In vivo administration of the same mAb H81.9 after transplantation of unmanipulated autologous marrow results in graft failure. In vitro mAb H81.9 inhibited colony formation from short-term and long-term marrow cultures.

METHODS AND RESULTS

We investigated the effect of another mAb, Ca1.41, which also recognizes nonpolymorphic determinants on human (HLA-DR) and canine major histocompatibility complex class II antigens but is reactive with a narrower spectrum of cells in both canine peripheral blood and marrow than mAb H81.9 (and other anti-HLA-DR mAbs). In contrast to all other anti-HLA-DR mAbs tested, Ca1.41 did not interfere with colony formation in short-term or long-term marrow cultures and spared a population of small mononuclear cells with low forward light scatter that was eliminated via apoptosis by exposure to mAb H81.9. These target cells included lymphocytes and CD34+ hemopoietic precursors that expressed MHC class II molecules as determined by mAb H81.9 but not by mAb Ca1.41. In addition, transmembrane signaling and up-regulation of interleukin-1beta mRNA occurred with mAb H81.9 but not with Ca1.41. Transplantation of autologous marrow treated in vitro cytolytically with mAb Ca1.41 allowed for complete hematopoietic reconstitution. Further, in vivo administration of Ca1.41 posttransplant did not lead to autologous graft failure as had been observed with mAb H81.9.

CONCLUSIONS

These results support the notion that major histocompatibility complex class II is expressed on early hematopoietic precursor cells but recognition is dependent upon the mAb used. Preliminary studies show that mAb H81.9 triggered transmembrane signaling, resulting in up-regulation of interleukin-1beta and apoptosis, although mAb Ca1.41 did not. The fact that Ca1.41 binding was modified in the presence of exogenous invariant chain-derived peptide suggests that both binding and signaling are peptide dependent.

Induction of negative regulators of haematopoiesis in human bone marrow cells by HLA-DR cross-linking

Tumour necrosis factor-alpha (TNF alpha) is up-regulated by cross-linking of major histocompatibility complex (MHC) class II [human leucocyte antigen (HLA)-DR] antigens on monocytes. This is done by a bacterial superantigen or anti-HLA-DR monoclonal antibody (MAb). We have previously shown that HLA-DR cross-linking results in inhibition of haematopoiesis and apoptosis. TNF alpha acts as a negative regulator of haematopoiesis. Here we investigated whether HLA-DR-mediated inhibition of haematopoiesis involved TNF alpha and TNF alpha-dependent secondary signals. Anti-HLA-DR MAb H81.9 up-regulated TNF alpha, as well as transforming growth factor beta, interleukin (IL)-1beta and IL-6 in human marrow cells at the ribonucleic acid (RNA) and protein level. The effect on TNF alpha was investigated further. Up-regulation was blocked by herbimycin A, consistent with a tyrosine kinase-dependent mechanism. Up-regulation was also blunted by the soluble TNF-receptor fusion protein TNFR:Fc, suggesting an autocrine amplification loop. Following TNF alpha up-regulation, there was increased expression of Fas (CD95) and Fas-ligand (Fas-L). Up-regulation of Fas and Fas-L was blocked by TNFR:Fc. Furthermore, MAb H81.9-induced apoptosis was prevented by anti-TNF alpha MAb and by the soluble Fas receptor, Fas-Ig, providing further evidence that the TNF effect was mediated via Fas. At the transcriptional level, cross-linking of HLA-DR by MAb H81.9 affects nuclear localization of NFkappaB, which is involved in the transcription of TNF alpha. NFkappaB activity is modified by changes in cellular redox potential, and we have shown that H81.9 affects redox potential as determined by the generation of nitric oxide. These data show that HLA-DR-initiated signals are able to trigger a cascade of negative regulators of haematopoiesis. This model provides an opportunity to dissect signalling pathways that may be involved in the development of spontaneous marrow failure, and to devise interventions aimed at protecting haematopoiesis.

DLA-DRB1 polymorphisms in dogs defined by sequence-specific oligonucleotide probes (SSOP)

To date, DNA sequences for 29 dog DLA-DRB1 alleles have been reported. However, no data exists on the frequencies of these alleles within the general dog population, nor is there any indication of whether there is interbreed variation of allele distribution. We have addressed this by establishing a molecular based sequence-specific oligonucleotide probing (SSOP) method to identify all of the known broad DRB1 types and we have used this to type a random panel of dogs. A series of oligonucleotide probes were designed to detect known polymorphisms in the three DRB1 hypervariable regions, together with two distinctive motifs in other regions of exon 2. This set of probes enabled us to assign broad DRB1 types. Two hundred and eighteen dogs were SSOP typed for DRB1. All but 4 of the published DLA-DRB1 alleles were identified in these animals. Interbreed variation in both allele distributions and allele frequencies were observed, which may be useful in the study of genetic variation between breeds. This variation also has implications for the selection of control groups for studies aimed at identifying MHC associations with disease susceptibility in the dog.

Immunohistochemical characterization of inflammatory cells in brains of dogs with granulomatous meningoencephalitis

The inflammatory cells of eleven dogs with canine granulomatous meningoencephalitis were characterized immunohistochemically. Macrophages were identified by antibodies directed against lysozyme and the DH82 antigen (expressed by cells of a malignant histiocytosis). T cells were demonstrated by CD3, CD43, and CD45R antigen, and B cells by immunoglobulin G and immunoglobulin M expression. Furthermore, staining for the major histocompatibility complex (MHC) class II antigen was evaluated. Diseased animals ranged from 1 to 9 years of age. Small and medium-sized breeds were affected predominantly. Lesions were widespread and localized mainly in the brain stem, less frequently in the cerebrum or cerebellum. Alterations were represented by perivascular cuffs, parenchymal granulomas, and leptomeningeal infiltrates. Lymphocytes and macrophages comprised the dominant cell populations; their percentage varied substantially between different animals and between sections from the same individual. Immunohistochemically, the bulk of lymphocytes were CD3 antigen-positive T cells, while only a few cells were CD43 and CD45R antigen-positive or were classified as B cells. The majority of macrophages expressed both lysozyme and DH82 antigen; however, some were positive for only one antigen. MHC class II antigen-expression, observed only within and in close proximity to the lesions, was found on all inflammatory cells, pericytes/endothelial cells, and microglia. Results were negative for canine distemper virus antigen and nucleoprotein mRNA, rabies virus antigen, fungi, bacteria, and protozoal agents. This immunomorphologic study reveals that inflammatory lesions in canine granulomatous meningoencephalitis consist of a heterogeneous population of MHC class II antigen-positive macrophages and predominantly CD3 antigen-positive lymphocytes. The data suggest a T cell-mediated delayed-type hypersensitivity of an organ-specific autoimmune disease as a possible pathogenic mechanism for this unique canine brain lesion.

Quantitative and qualitative immunohistochemistry of T cell subsets and MHC class II expression in the canine small intestine

In man and rodents, cells of the gastrointestinal immune system include B and T lymphocytes, granulocytes, macrophages and dendritic cells. Abnormalities in leucocyte numbers and function have been described in diseases of humans, such as coeliac disease and inflammatory bowel disease. The purpose of this study is to describe the normal distribution of T cells and MHC Class II expression in the small intestine of clinically normal dogs, to allow subsequent comparison with disease states. Full-thickness sections of duodenum, jejunum and ileum from seven young adult beagle dogs were immediately snap-frozen following euthanasia. Avidin-biotin-enhanced immunocytochemistry was used to detect expression of canine CD3, CD4, CD8 and MHC Class II antigens. Positively stained lamina propria cells were quantified using an eyepiece graticule, and positively stained intraepithelial cells by counts per 100 epithelial cells. In the lamina propria, the density of all leucocyte subsets was significantly increased towards the villus tip for all regions (p < 0.05). There was no apparent difference in the distribution of CD3+, CD4+ and CD8+ leucocytes between the three portions of the small intestine. The ratios of CD4+ cells to CD8+ cells in the lamina propria and epithelium were 59:41 and 15:85, respectively. Subtractive analysis suggested that 50-55% of CD3+ intraepithelial cells were CD4-CD8-. MHC Class II expression was apparent upon lamina propria cells with a dendritic morphology, as well as round cells. Epithelial MHC Class II expression was apparent in 7/7 ileal sections, compared with only 1/7 duodenal and 1/7 jejunal sections. This study shows that the small intestinal mucosa of the dog contains similar leucocyte populations to those found in other species, and suggests that these cells may play similar roles in gastrointestinal immunity.

Immunophenotyping of canine bronchoalveolar and peripheral blood lymphocytes

The immunophenotype of canine lymphocytes obtained by bronchoalveolar lavage (BAL) was investigated and compared with that of peripheral blood leukocytes (PBL). Indirect immunofluorescence, generated by monoclonal antibodies (mAb) specific for canine CD5, CD4, CD8, CD45pan, CD45RA, MHCII and THY-1, was detected by flow cytometry. In comparison with PBL, in BAL there are fewer lymphocytes positive for CD45RA (75.4 +/- 12.6% vs. 42.3 +/- 9.4%; P < 0.05) and MHCI I (97.0 +/- 2.9% vs. 74.0 +/- 7.6%; P < 0.01), while there are more cells positive for CD8 (19.0 +/- 3.6% vs. 29.5 +/- 12.0%; P < 0.05). Thus there is a lower CD4/CD8 ratio in the cell compartment accessible by BAL (2.2 +/- 0.3 vs. 1.3 +/- 0.6; P < 0.005). The immunophenotype may be stable over time, as indicated by reexamination of cells obtained from one dog at four times over 1 year. Investigating the phenotype of lymphocytes from three different locations of the right lung, the cranial lobe lymphocytes show a lower CD4/CD8 ratio in comparison with PBL (1.81 +/- 0.35 vs. 1.12 +/- 0.31, n = 5; P < 0.02). In general, less MHCII positive lymphocytes (P < 0.001) and greater immunophenotype variability of results were found in these separate samples compared with pooled samples from these locations.

Up-regulation of IL-2 receptor alpha and MHC class II expression on lymphocyte subpopulations from bovine leukemia virus infected lymphocytotic cows

Infection with bovine leukemia virus (BLV) leads to a persistent lymphocytosis (PL) characterized by a marked increase in circulating B lymphocytes that express the orthologue of CD5. To gain insight into the factors accounting for lymphocytosis, experiments were conducted to determine the functional activation status of lymphocytes from BLV seronegative and BLV infected aleukemic cows with PL. Stimulation with the B lymphocyte mitogen Staphylococcus aureus Cowan strain I (SAC), recombinant human interleukin-2 (rIL-2), or pokeweed mitogen (PWM), a T lymphocyte-dependent B lymphocyte mitogen, revealed differences in the pattern of expression of IL-2 receptor alpha (IL-2R alpha) and major histocompatibility (MHC) class II molecules on B and T lymphocytes from uninfected and BLV infected PL cows. rIL-2 induced expression of IL-R alpha on B lymphocytes from PL cows but not B lymphocytes from BLV seronegative cows. SAC alone, or in combination with rIL-2, had no effect on B lymphocytes from BLV seronegative cows. However, rIL-2 alone or in combination with SAC induced expression of IL-2R alpha on B lymphocytes from PL cows. PWM stimulated expression of IL-2R alpha on bovine B lymphocytes regardless of BLV status, and induced a significantly higher level of expression on B lymphocytes from PL cows. Mitogens and rIL-2 had a similar stimulatory effect on induction of IL-2R alpha expression on CD4 T lymphocytes regardless of BLV status. Only PWM induced expression of IL-2R alpha on bovine CD8 T lymphocytes and induced a significantly higher level of expression on this T lymphocyte subset from PL cows. Examination of freshly isolated B lymphocytes from PL cows revealed increased spontaneous expression of the MHC class II molecule compared to B lymphocytes from control cows. None of the culture conditions examined induced MHC-II expression on CD4 and CD8 T lymphocytes from BLV seronegative cows. In contrast, SAC+IL-2 and PWM induced MHC-II expression on CD4 and CD8 T lymphocytes from BLV infected PL cows, resulting in a significantly greater proportions of these lymphocyte subsets expressing this molecule compared to CD4 and CD8 T lymphocytes from control cows. The data indicate that infection with BLV affects the response of B and T lymphocytes to signals of activation, up-regulating the expression of surface molecules involved in both direct contact and cytokine-mediated T lymphocyte-dependent B lymphocyte activation.

Abnormalities of lymphocyte subsets in canine systemic lupus erythematosus

Canine systemic lupus erythematosus (SLE) is a disease clinically very similar to its human counterpart. But so far, no study has reported an accurate evaluation of the lymphocyte subsets in the canine disease. Here, we present a study in which lymphocyte subsets have been evaluated in the peripheral blood of 20 dogs suffering from spontaneous systemic lupus erythematosus (SLE) in active and inactive phases, before and during treatment with prednisone and levamisole. 22 healthy dogs have been used as a control population. We show that canine SLE in active phases is associated with a several lymphopenia (1050 +/- 520 10(6) cells/l versus 2130 +/- 1 020 10(6) cells/l in controls). A striking finding is the imbalance of the CD4 and CD8 subsets (respectively 56.7 +/- 10.7% and 10.9 +/- 3.8% of CD4+ and CD8+ lymphocytes versus 40.5 +/- 11.5% and 18 +/- 4.4% in controls) and a strong activation of T-cells in active phases (64.1 +/- 16.9% of 2B3+ cells versus 46.5 +/- 16.7%). Moreover, we observed a persistence of the T subset imbalance during spontaneous evolution. In contrast, the treatment induced in dogs showing a good response the correction of CD4/CD8 ratio and no clinical manifestations, whereas in low responders no such improvements were observed. Thus, this work suggests that the main immunological imbalance seen in SLE could be associated with defective suppressor cells and provides further evidence of similarity of human and dog SLE.

Persistent upregulation of MHC Class II antigen expression on T-lymphocytes from cats experimentally infected with feline immunodeficiency virus

A significant elevation in the percentage of CD4+ and CD8+ T-lymphocytes expressing major histocompatibility complex (MHC) Class II antigens was observed in the blood of cats shortly after they were experimentally infected with feline immunodeficiency virus (FIV). In addition to an increase in the relative proportion of T-lymphocytes expressing Class II antigens, there was an increase in the density of Class II antigens on the cell surface. These elevations were still evident at the completion of the 5 month study. A second group of cats that had been infected with FIV for almost 5 years, and with either normal or abnormally low levels of CD4+ T-lymphocytes, had similar elevations in MHC II expression, suggesting that such abnormalities are lifelong. Cats with chronic (2 year) feline leukemia virus (FeLV) infection or dual FIV/FeLV infections also showed similar alterations in MHC II expression on CD4+ and CD8+ T-lymphocytes, suggesting that these alterations were not FIV specific. Feline T-lymphocytes expressed more MHC II antigen and interleukin-2 (IL-2) receptor following stimulation in vitro with conconavalin A and IL-2, demonstrating that feline T-lymphocytes respond to activation signals in a manner similar to T-lymphocytes of other species. However, changes in MHC II expression on T-cells of FIV infected cats were not explainable by viral induced T-cell activation alone, because FIV infected cats with elevated MHC II expression did not have coincident elevations in IL-2 receptor expression.

Immunological characterization of canine hematopoietic progenitor cells

Canine hematopoietic progenitor cells were characterized by separation with monoclonal antibodies. Depleted and enriched fractions were studied for growth of CFU-GM in semisolid agar and for repopulating capacity of lethally irradiated dogs. CFU growth was not reduced by depletion of marrow using monoclonal antibodies F 3-20-7 (anti-dog Thy-1), MT606 (anti-human CD 6), and IOT2a (anti-human DR). CFU growth was variable following treatment with the anti-canine T-cell antibody MdT-P 1 and immunomagnetic bead separation. It was regularly enriched when MdT-P 1 treatment was followed by immunorosetting with staphylococcal protein A-loaded sheep red blood cells and density gradient separation. Lethally irradiated dogs were reconstituted by autologous marrow depleted of MdT-P 1-positive cells using immunorosetting and density gradient centrifugation, whereas immunomagnetic bead-depleted marrow was ineffective. Fluorescence-activated cell sorting showed enrichment of hematopoietic progenitor cells in the weakly MdT-P 1-positive fraction.

Functional characterization of canine lymphocyte subsets

Functional characterization of subsets of T lymphocytes is essential for transplantation studies in dogs, as it is in other species. We studied the function of T cells separated by two mouse monoclonal antibodies recognizing complementary subsets--an antibody directed to canine T cells (MdT-P1) with an up-regulating function, and an antibody directed to human CD 8 (MT811) that cross-reacts with down-regulating canine T cells. Immunorosetting with sheep red blood cells and Percoll gradient allowed us to study depleted and enriched fractions. Their function was tested in mixed lymphocyte culture (MLC), cell-mediated cytotoxicity (CML), and coculture with B cells in a hemolytic plaque assay (PFC). In MLC, MdT-P1-positive cells showed a high proliferative response, and MT811-positive cells responded poorly to allogeneic cells. Vice versa, MT811- negative cells responded strongly, and MdT-P1-negative cells were poor responders but strong stimulators. Effector cells of CML were separated following 8 days of culture and prior to mixing with target cells. Enriched and depleted fractions with either antibody showed low cytotoxic activity as compared with unseparated cells. When added to unseparated effector cells MT 811-positive cells suppressed cytotoxicity. B cells were obtained by rosetting with staphylococcal protein A (SPA). Their immunoglobulin production was studied following 6 days of culture stimulated by pokeweed mitogen in a reverse hemolytic plaque assay. Again, MT 811-positive cells added to the culture suppressed, and MT 811-negative cells enhanced immunoglobulin production. In conclusion, immunorosetting with two monoclonal antibodies allowed us to distinguish subpopulations of canine T cells with up-regulating (helper/inducer) from those with down-regulating (suppressor) activity.

Recognition of monocyte-associated antigens in the dog

Canine pregnant sera were investigated for monocyte-specific cytotoxic antibodies against a cell panel from 50 unrelated dogs. Contaminating DLA and DLB reactivity was removed by absorption on a random pool of purified lymphocytes. Two monocyte-associated antigens were recognized by two independent clusters of antisera; the existence of further antigens is suggested. In preliminary segregation studies, the inheritance of these determinants in linkage with DLA could not be observed.

Distribution of MHC class II antigens in feline tissues and peripheral blood

A new monoclonal antibody raised against gradient-purified feline immunodeficiency virus was found to recognize a bimolecular complex, comprising 27-29 kD and 32-35 kD subunits, on feline peripheral blood lymphocytes. Immunoperoxidase staining of feline tissues with this antibody, designated 43.2H2, demonstrated a reactivity pattern similar to that described for MHC II antigens of the dog, horse, and pig, but differed from human and mouse in having staining of T-cell zones in spleen and lymph nodes. Flow cytometric analysis revealed that 42.3H2 reacted with 88.97% +/- 16.00% of feline peripheral blood lymphocytes (n = 20). This high level of reactivity was found to be consistent by repeated sampling over a 4-month period. Two-color flow cytometric analysis was used to determined the reactivity pattern on lymphocyte subsets: 88.92% +/- 7.30% of CD4+ lymphocytes were 42.3H2-positive, while 85.99% +/- 11.46% of CD8+ cells were positive (n = 11 for both). B lymphocytes had the highest reactivity (99.47% +/- 0.45; n = 9) and also had the highest fluorescence intensity. By gating based on light scatter properties, 95.06% +/- 7.35% of monocytes were 42.3H2-reactive (n = 18), while granulocytes were negative.

MHC class II antigens on canine bronchoalveolar cells

To evaluate the expression of MHC (major histocompatibility complex) antigens on canine bronchoalveolar cells (BAC), bronchoalveolar lavages (BAL) were performed in mongrel and German shepherd dogs. MHC class II antigens on canine BAC and peripheral blood mononuclear cells (PBMC) were detected by monoclonal antibodies (mAbs) B1F6, 7.5.10.1 and Q5/13 recognising canine MHC class II antigens, using cytofluorometry. These mAbs reacted with more than 20% of BAC and PBMC in both breeds of dog. The percentage of MHC class II positive cells in BAC were lower than those in PBMC. There was no significant difference in the percentages of MHC class II positive BAC and PBMC in mongrel and German shepherd dogs. To further identify the expression of MHC class II antigens on BAC, the cells were separated into adherent and nonadherent cells by petri dish adherence. The percentages of MHC class II positive cells in adherent and non-adherent cell populations were similar. Nearly half the lymphocytes in normal BAC were T cells detected by mAbs F3-20-7 and 1A1; B cells were scarce and represented less than 10% of nonadherent cells. Immunoprecipitation by anti-MHC class II mAbs, and SDS-polyacrylamide gel electrophoresis (SDS-PAGE) revealed MHC class II-like molecules on canine BAC and PBMC. After stimulation with phytohaemagglutinin (PHA), the percentages of class II positive cells in BAC and PBMC were significantly increased. Thus, these anti-MHC class II mAbs may prove to be of advantage in experiments designed to evaluate the changes in class II antigen expression on canine BAC during the course of immune response in the lung, as in pulmonary allograft rejection.

Supernatants of human leukocytes contain mediator, different from interferon gamma, which induces expression of MHC class II antigens

In this report, data are presented on the regulation of MHC class II antigen expression by a mediator present in supernatants of human mixed leukocyte cultures (MLC-SN), and which is different from IFN-gamma. The capacity of supernatants to induce antigen expression did not correspond to titers of IFN-gamma. Removal of IFN-gamma using either dialysis against pH 2 or neutralizing mAb against human IFN-gamma did not abrogate the MHC class II antigen expression-inducing capacity of MLC-SN when tested on adenocarcinoma cell lines, kidney epithelial cells, and fibroblasts in vitro in an indirect immunofluorescence assay. Therefore, supernatants of human leukocytes contain a mediator, different from IFN-gamma, which induces expression of MHC class II antigens. Dose-response studies revealed that the mediator is produced after allogeneic and lectin stimulation of human leukocytes, and by unstimulated leukocytes. Activation of leukocytes resulted in increased titers of the mediator. The mediator markedly enhances expression of both HLA-DR and HLA-DQ antigens, whereas IFN-gamma had a similar effect on HLA-DR antigens, and only a minor effect on HLA-DQ antigens. Interaction of the mediator and IFN-gamma resulted in a potentiating effect of these two factors on MHC class II antigen expression. Biochemical analysis revealed a mediator, distinguishable by FPLC from IL-1, IL-2, and human IFN-gamma, and which has a molecular mass of 32 kD.