A biochemical characterization of feline MHC products: unusually high expression of class II antigens on peripheral blood lymphocytes

Polymorphisms and tissue expression of the feline leukocyte antigen class I loci FLAI-E, FLAI-H, and FLAI-K

Cytotoxic CD8+ T-cell immunosurveillance for intracellular pathogens, such as viruses, is controlled by classical major histocompatibility complex (MHC) class Ia molecules, and ideally, these antiviral T-cell populations are defined by the specific peptide and restricting MHC allele. Surprisingly, despite the utility of the cat in modeling human viral immunity, little is known about the feline leukocyte antigen class I complex (FLAI). Only a few coding sequences with uncertain locus origin and expression patterns have been reported. Of 19 class I genes, three loci--FLAI-E, FLAI-H, and FLAI-K--are predicted to encode classical molecules, and our objective was to evaluate their status by analyzing polymorphisms and tissue expression. Using locus-specific, PCR-based genotyping, we amplified 33 FLAI-E, FLAI-H, and FLAI-K alleles from 12 cats of various breeds, identifying, for the first time, alleles across three distinct loci in a feline species. Alleles shared the expected polymorphic and invariant sites in the α1/α2 domains, and full-length cDNA clones possessed all characteristic class Ia exons. Alleles could be assigned to a specific locus with reasonable confidence, although there was evidence of potentially confounding interlocus recombination between FLAI-E and FLAI-K. Only FLAI-E, FLAI-H, and FLAI-K origin alleles were amplified from cDNAs of multiple tissue types. We also defined hypervariable regions across these genes, which permitted the assignment of names to both novel and established alleles. As predicted, FLAI-E, FLAI-H, and FLAI-K fulfill the major criteria of class Ia genes. These data represent a necessary prerequisite for studying epitope-specific antiviral CD8+ T-cell responses in cats.

Characterization of class I bovine lymphocyte antigens (BoLA) by one-dimensional isoelectrofocusing

BoLA class I antigens were characterized in a group of British and Dutch Friesian cattle by one-dimensional isoelectric focusing (1D-IEF) and the results compared with serology using alloantisera and microcytotoxicity. For IEF analysis, non-stimulated peripheral blood mononuclear cells (PBM) were metabolically labelled with 35S methionine, detergent lysates were prepared and MHC molecules precipitated with the monoclonal antibodies (mAbs) W6/32 or B1.1G6. Staphylococcus protein A precipitated antigens were separated on a vertical slab gel under denaturing conditions. The banding patterns seen for the W6/32 precipitated molecules obtained by 1D-IEF were compared with the serological specificities. Characteristic banding patterns were observed for most serological specificities as well as workshop undefined haplotypes. These patterns were seen both in families and the outbred population. In families IEF haplotypes segregated with serotypes. Additional MHC class I products were suggested by variable banding patterns for different w10 haplotypes and when using the different mAbs. A pulse chase experiment with a w12 animal also suggested more than one expressed product. The w2 and w5 specificities were not precipitated by either W6/32 or B1.1G6 and w6.2 and w6.4 were precipitated by W6/32 but not by B1.1G6. These results show that 1D-IEF is useful for BoLA typing. For the characterization of class I antigens, however, much depends on the mAbs used.

Molecular characterisation and expression of CD4 in two distantly related marsupials: the gray short-tailed opossum (Monodelphis domestica) and tammar wallaby (Macropus eugenii)

The gene and corresponding cDNA for CD4 in the gray short-tailed opossum, Monodelphis domestica, and the cDNA sequence for CD4 in the tammar wallaby, Macropus eugenii, have been characterised. The opossum CD4 homolog reveals conserved synteny, preserved genomic organisation and analogous structural arrangement to human and mouse CD4. Opossum and tammar CD4 exhibit typical eutherian CD4 features including the highly conserved p56(lck) binding motif in the cytoplasmic region and the invariant cysteine residues in extracellular domains 1 and 4. Interestingly, the marsupial CD4 sequences substitute a tryptophan for the first cysteine in domain 2 negating the formation of a disulphide bond as seen in other eutherian CD4 sequences except human and mouse. Overall the marsupial CD4 sequences share amino acid identity of 59% to each other and 37-41% with eutherian mammals. However, in contrast to eutherian homologs, the marsupial CD4 sequences were found to be truncated at the terminal end of the cytoplasmic tail. This is the first report confirming the presence of CD4 in a marsupial and describing its key features.

Cloning, expression, and characterization of fugu CD4, the first ectothermic animal CD4

We have cloned and sequenced the first ectothermic animal CD4 gene from fugu, Takifugu rubripes, using a public database of the third draft sequence of the fugu genome. The fugu CD4 gene encodes a predicted protein of 463 amino acids containing four extracellular immunoglobulin (Ig)-like domains, a transmembrane region, and a cytoplasmic tail. Fugu CD4 shares low identity of about 15-20% with avian and mammalian CD4 proteins. Unlike avian and mammalian CD4, fugu CD4 lacks the Cys pair of the first Ig-like domain, but has a unique possible disulfide bond in the third domain. These differences suggest that fugu CD4 may have a different structure that could affect binding of major histocompatibility complex class II molecules and subsequent T-cell activation. In the putative fugu cytoplasmic region, the protein tyrosine kinase p56lck binding motif is conserved. The predicted fugu CD4 gene is composed of 12 exons, differing from other CD4 genes, but showing conserved synteny and many conserved sequence motifs in the promoter region. RT-PCR analysis demonstrated that the fugu CD4 gene is expressed predominantly in lymphoid tissues. We also show that fugu CD4 can be expressed on the surface of cells via transfection. Molecular characterization of CD4 in fish provides insights into the evolution of both the CD4 molecule and the immune system.

Recycling MHC class I molecules and endosomal peptide loading

MHC class I molecules usually present peptides derived from endogenous antigens that are bound in the endoplasmic reticulum. Loading of exogenous antigens on class I molecules, e.g., in cross-priming, sometimes occurs, but the intracellular location where interaction between the antigenic fragment and class I takes place is unclear. Here we show that measles virus F protein can be presented by class I in transporters associated with antigen processing-independent, NH(4)Cl-sensitive manner, suggesting that class I molecules are able to interact and bind antigen in acidic compartments, like class II molecules. Studies on intracellular transport of green fluorescent protein-tagged class I molecules in living cells confirmed that a small fraction of class I molecules indeed enters classical MHC class II compartments (MIICs) and is transported in MIICs back to the plasma membrane. Fractionation studies show that class I complexes in MIICs contain peptides. The pH in MIIC (around 5.0) is such that efficient peptide exchange can occur. We thus present evidence for a pathway for class I loading that is shared with class II molecules.

Variable expression of major histocompatibility complex class II in the domestic cat

This paper describes the characterisation of six independently produced monoclonal antibodies (mAbs) specific for non-polymorphic determinants of feline major histocompatibility complex (MHC) class II. One mAb is an anti-sheep class II which cross-reacts with the cat and five have been produced in response to immunisation with purified feline immunodeficiency virus. Despite their independent source all the mAbs have identical reactivities, immunoprecipitating two complex groups of polypeptides of M(r) 33 to 36.000 (MHC class II alpha chains) and M(r) 28 to 31,000 (MHC class II beta chains). Immunoblot analysis showed them to be beta chain-specific. One and two-dimensional electrophoresis revealed the complexity of feline class II mass and charge and implied the expression of multiple class II loci in the cat. Furthermore, it was demonstrated that distinct cell populations expressed a distinct range of class II variants. This suggesting either the differential expression or the distinct post-translational modification of lymphocytes from different sites. The mAbs have also been used for the detailed examination of the cellular distribution and tissue localisation of MHC class II in the cat.

Uterine carcinomas in mother cats after intrafetal inoculation of allogeneic tumor cells (K248 C and P)

Three out of 13 queens that had undergone injection of tumor cells from an allogeneic feline mammary carcinoma cell line through the wall of the pregnant uterus developed a carcinoma of the uterus. The possible role of immune tolerance associated with pregnancy and/or major histocompatibility complex (MHC) compatibility is discussed.

Vaccination against feline immunodeficiency virus using fixed infected cells

Crandell feline kidney cells and feline thymocytes, either feline immunodeficiency virus (FIV) infected or uninfected, were fixed with paraformaldehyde and used to vaccinate cats. The cells were mixed with a 30:70 water/mineral oil emulsion containing 250 micrograms ml-1 N-acetyl-D-glucosaminyl-beta-(1-4)-N-acetyl-muramyl-L-alanyl-D-isoglutam ine. Eighteen specific pathogen-free cats were vaccinated three times with 3-week intervals and challenged 21 days after the final boost with a low dose of the homologous FIV-UT113 strain. Eight out of ten cats that had received FIV-infected cell vaccines developed significant anti-FIV antibody titres to the envelope and core antigens. Neutralizing antibodies were detectable at the moment of challenge in the sera of these animals. Within 5 weeks after challenge 15 out of 18 cats became viraemic. Three animals, two that had been vaccinated with FIV-infected thymocytes and did not develop antibody, and one that had received an uninfected thymocyte preparation, remained uninfected for 6 months. Upon rechallenge of the three animals, two again resisted infection; these cats had been immunized with the infected and the uninfected thymocyte preparations, respectively.

Biochemical definition of DLA-A and DLA-B gene products by one-dimensional isoelectric focusing and immunoblotting

The serologically defined canine MHC gene products (DLA-A and DLA-B) were investigated by one-dimensional isoelectric focusing after detergent phase separation, and immunoblotting (1D-IEF). The animals studied (n = 36) represented three different breeds. Since DLA-A and DLA-B antigens are MHC class I and class II molecules, respectively, cross-reactive polyclonal antibodies specific for human class I or class II molecules were utilized to visualize the protein pattern. The relative positions of the bands were correlated with the DLA-A and DLA-B antigens. In most cases DLA antigens of identical serological type did not differ in their 1D-IEF pattern except for DLA-A9 and the serologically undefined DLA-B gene product DLA-B 'blank'. For DLA-A9, two subtypes (A9.1 and A9.2) were identified in Beagle and associations of A9.1 with the haplotype A9,B4 and of A9.2 with A9,B6 were seen. In contrast, the haplotype A9,B6 in Labradors was associated with A9.1. Whereas all six serologically defined DLA-A antigens possessed distinct isoelectric points (IEP), not all DLA-B antigens could be differentiated by 1D-IEF:B5 as well as B13 coband with one B 'blank' specificity (BE1). Furthermore, a second B 'blank' (BE2) could be identified by 1D-IEF, underlining the advantage of this technique in the immunogenetic analysis of DLA gene products in dogs.

Immunoreactivity of the central nervous system in cats with a Borna disease-like meningoencephalomyelitis (staggering disease)

The inflammatory cell composition and the expression of major histocompatibility complex (MHC) antigens in the central nervous system (CNS) of 13 cats with a spontaneous, Borna disease-like meningoencephalomyelitis (staggering disease) was investigated by immunohistochemistry with a panel of monoclonal and polyclonal antibodies. T lymphocytes were the predominating inflammatory cells within the adventitial space. CD4+ T cells were more abundant than CD8+ T cells. Scattered IgG-, IgA- and IgM-containing cells were found in the adventitial space and surrounding neuropil, often adjacent to neurons. There was a markedly increased MHC class II expression in cells morphologically resembling microglia. In several cats, Borna disease virus specific antigen was detected, but only in a few cells, mainly of macrophage character. Our findings indicate a long-standing inflammatory reaction in the CNS of cats with staggering disease, possibly triggered and sustained by a persistent viral infection.

Serological and biochemical detection of B-cell antigens in goats

The production of B-cell specific alloantisera by lymphocyte transfusion between class I matched, MLR positive goats is described. Furthermore, the usefulness of preceding IEF typing is demonstrated in the selection of immunization pairs. After suitable absorptions and cluster analysis the detected B-cell specific antigens were designated BeD1-BeD6. The specificity BeD3 could also be detected by two class II-specific murine anti-H2 monoclonal antibodies. IEF class II typing of 34 animals gave concordant results between the two techniques. One additional allelic variant could be detected by IEF typing. The detected products segregated in close linkage to the earlier described caprine class I antigens. One recombinant has been found in 78 offspring. The reactivity of cells in mixed lymphocyte cultures (MLC) was correlated with the compatibility of the test cells for their B-cell specific antigens. Three of the B-cell specific sera were characterized by immunoprecipitation. The precipitated antigens corresponded in molecular weight to MHC class II products as described in other species indicating that the here described caprine products are of class II nature.

An immunohistological study of cutaneous lymphocytes in vitiligo

In a study of 49 biopsies from the margins of depigmented cutaneous lesions in 18 patients with vitiligo, highly significant overall increases were found in CD3+, CD4+, and CD8+ T cells, though cell numbers in individual cases were often within the normal range. Many of the T cells were activated (MHC class II+, interferon gamma+), of CD45RO (UCHL1+) memory subset, and many expressed the cutaneous lymphocyte-associated antigen (HECA-452+) typical of skin-homing T cells. Immunohistologically, the most intense epidermal T-cell infiltration was present within 0.6 mm of the edge of the lesion in 10 of 13 double-stained sections with a clearly defined zone of melanocyte depletion. In 40 lesions from 17 patients seen 11-64 weeks after biopsy, no apparent association was found between T-cell numbers and disease activity as assessed by Köbnerization of biopsy wounds or spread of depigmentation. These findings are consistent with the hypothesis that lesional T cells rather than circulating antimelanocytic antibody may be responsible for the supposedly autoimmune but characteristically patchy destruction of cutaneous melanocytes in vitiligo. Nevertheless, many of the infiltrating T cells are probably innocent bystanders attracted by upregulated cell adhesion molecules near sites of melanocyte damage.

Vigilin is a cytoplasmic protein. A study on its expression in primary cells and in established cell lines of different species

A fusion protein composed of about two vigilin domains and beta-galactosidase was used to raise polyclonal antibodies which were affinity-purified and employed for immunoblotting and immunohistochemistry. A protein of an apparent molecular mass of 155 kDa could be stained in extracts of a variety of cells from different species and organs. Immunohistological studies on single cells showed that vigilin is accumulated in the cytoplasm. During in vitro maintenance of primary cell cultures, as well as of a growth-factor-dependent cell line, vigilin expression decreases and ceases in senescent cells. In contrast, vigilin is constitutively expressed in all other transformed cell lines of various origin studies so far. Vigilin expression can be induced in peripheral blood lymphocytes by mitogen stimulation. These observations suggest an involvement of vigilin in processes of cell activation. Immunoblot experiments demonstrating the presence of vigilin in a broad range of eukaryotes, indicate a high degree of evolutionary conservation.

Polymorphism and estimation of the number of MhcCyca class I and class II genes in laboratory strains of the common carp (Cyprinus carpio L.)

Restriction fragment length polymorphisms (RFLPs) have been identified in the Mhc of the carp (MhcCyca) using class I (Cyca-Z) and class II (Cyca-YB) specific probes. The K1-5 and K2-1 probes were obtained as PCR products after amplification of genomic DNA from a European carp using primers deduced from genomic sequences, and were shown to be 90% and 80% similar to Cyca-Z exon 3 and Cyca-YB exon 2 sequences, respectively. Six carp strains of different geographical origins and genomic status were studied. In homozygous gynogenetic carp strains the class I probe K1-5 hybridized to 9-12 fragments, whereas the class II probe K2-1 hybridized to 3-5 fragments. Thus, the Cyca consists of multiple class I and class II genes. The level of polymorphism of the Cyca genes of the strains studied was calculated as the percentage of polymorphic fragments among the total number of fragments observed, and was shown to be 70% for class I and 40-66% for class II genes. In addition, a possible correlation was investigated between a serologically defined locus K, which was demonstrated previously to incorporate class I-like characteristics, and molecular genotyping using the class I probe. Two gynogenetic families, which were serologically typed K1 and K2 homozygous, also differed in their RFLPs using a class I probe. This would suggest that the K locus is part of the Cyca complex.

Abnormal expression of MHC class II and ICAM-1 by melanocytes in vitiligo

The relationship between damage to cutaneous melanocytes and antimelanocyte autoimmunity in vitiligo is unclear. We have demonstrated abnormal expression of MHC class II molecules by perilesional melanocytes in 13/21 patients with vitiligo and a six-fold increase in the number expressing the intercellular adhesion molecule ICAM-1. These molecules have important roles in normal antigen presentation and activation of helper T lymphocytes, and their expression by melanocytes may contribute to the abnormal immune response in vitiligo. MHC class II is not expressed by melanocytes in psoriasis and is unlikely to be induced in vitiligo by cytokines released from activated non-melanocyte-specific T lymphocytes.

Human cytomegalovirus in the pancreas of patients with type 2 diabetes: is there a relation to clinical features, mRNA and protein expression of insulin, somatostatin, and MHC class II?

Human cytomegalovirus (HCMV) was recently demonstrated in the pancreas of about half the patients with type 2 diabetes mellitus in the absence of mumps, rubella or Coxsackie B virus. The present study addresses the question as to whether type 2 diabetes with an HCMV-positive pancreas differs from those with HCMV-negative pancreases with respect to age, sex, treatment, duration of disease, volume densities of B-cells and D-cells, mRNA levels of insulin and somatostatin, islet amyloid peptide deposits and major histocompatibility complex (MHC) class I and class II gene transcription, and protein expression. HCMV-positive type 2 diabetic patients showed a tendency towards a shorter duration of disease and significantly increased levels of MHC class II on RNA. In addition, expression of MHC class II product (HLA-DR) was identified in duct epithelial cells and/or islet cells in 9 diabetic pancreases and in 2 non-diabetic glands. No MHC class I expression could be detected. No other clinical differences between HCMV-positive and HCMV-negative glands were found. All 10 HCMV-positive diabetics showed a strong expression of MHC class II mRNA in the pancreas. By immunocytochemistry, 4 of 10 demonstrated expression on the islets; three of ten also expressed MHC DR beta on ductal cells. This finding might be related to the viral infection, as only 2 of the 9 HCMV-negative patients were HLA-DR beta positive and none of the non-diabetic controls showed increased levels of MHC class II mRNA. These data suggest that HCMV infection in the pancreas is associated with type 2 diabetes. However, no conclusions as to a role of this virus in the aetiopathology of type 2 diabetes can be drawn at present.

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.

Immunohistochemical analysis of mucosal gamma-interferon production in coeliac disease

The role of gamma-interferon in the pathogenesis of enteropathies with an immunological basis such as coeliac disease, is unclear. Gamma-interferon immunoreactive lymphocytes were quantified in jejunal biopsies from patients with coeliac disease and from normal controls. In coeliac disease, there was an apparent decrease in the percentage of both intraepithelial (3.5% v 13.5%) and lamina propria (10.3% v 47.2%) lymphocytes expressing gamma-interferon compared with controls. In patients successfully treated with a gluten free diet, the percentage of gamma-interferon immunoreactive intra-epithelial lymphocytes was 10.3%. Intraepithelial lymphocytes were immunonegative for class II major histocompatibility complex, while epithelial cells showed increased expression of this product in coeliac disease. The results show that a relatively large proportion of lymphocytes in normal small bowel express gamma-interferon. They also indicate that in coeliac disease the major increase in the numbers of mucosal lymphocytes is the result of infiltration by lymphocytes not expressing gamma-interferon.

MHC class II molecules and immunoglobulins on peripheral blood lymphocytes of the bottlenosed dolphin, Tursiops truncatus

The immune system of marine mammals is of comparative interest because of its adaptation to the aquatic environment. Little information, however, is available on its cellular and molecular components. Here, we used a cross-reactive antibody to MHC class II molecules and an immunoglobulin-specific antiserum for identifying these molecular species on lymphocytes of the bottlenosed dolphin, Tursiops truncatus. Limited structural analyses indicated that class II molecules and immunoglobulins of dolphin closely resemble those of other vertebrates. In the peripheral blood of most land mammals both class II and immunoglobulins are usually found on B but not T lymphocytes. Expression of immunoglobulins on dolphin peripheral blood lymphocytes suggests a ratio of B cells to T cells comparable to that of land mammals. However, unlike the majority of land mammals, virtually 100% of the peripheral T cells display pronounced expression of class II molecules, generally considered an indication of T cell activation. It is therefore possible that the physiology of T cell activation has unusual attributes in the dolphin. It is especially interesting that some land mammals, namely swine (ungulates) and dogs and cats (carnivores), also express class II molecules on peripheral blood T lymphocytes. Since ungulates and carnivores are thought to share a common distant ancestry with toothed whales, the evolutionary history may be more relevant than the environmental history in determining these unusual attributes.

Characterization of the inflammatory infiltrate in ovarian dysgerminoma: an immunocytochemical study

The inflammatory infiltrate has been characterized in 10 cases of ovarian dysgerminoma using a panel of antisera to T-cells, B-cells and macrophages. The expression of Class II major histocompatibility complex (MHC) antigens and the distribution of interferons alpha and gamma were also examined. T-lymphocytes were present in all tumours, often closely admixed with neoplastic elements. T-cells in most areas were immunoreactive with gamma interferon. B-cells were generally scanty although germinal centres were present in three tumours. Immunocytochemistry revealed greater numbers of macrophages than had been appreciated on routinely stained sections. Macrophages were closely related to both lymphoid and tumour cells, and many macrophages were immunoreactive for alpha interferon. Class II MHC expression was mainly restricted to macrophages and B-cell areas although occasional T-cells were also stained. Dysgerminoma cells did not express Class II MHC antigens.

Feline immune system

Immunological features of feline lymphocytes, immunoglobulins, monocytes/macrophages, cytokines, major histocompatibility complex and delayed-type hypersensitivity are reviewed. Attention is given to the comparison of the feline immune system with the immune systems of humans and other animals. Also presented is information on the modification of feline immunity by pathogens.

Investigation of mink MHC (MhcMuvi) class I molecules by isoelectric focusing (IEF)

Mink (Mustela vision) class I leucocyte antigens, here abbreviated MhcMuvi according to the proposal given by Klein et al. (1990), were characterized by isoelectric focusing (IEF), using Triton X-114-extracted and neuraminidase-treated membrane proteins from spleen cells, followed by immunoblotting and development with a murine monoclonal antibody raised against denatured major histocompatibility complex (MHC) class I antigens. Muvi class I antigens were investigated in a group of 97 Danish mink (including five families), of six types (Standard, Wild, Pastel, Pearl, Violet and Sapphire), and a group of 110 French 'Wild' mink. For each mink type maximally six protein bands in IEF were identified. Standard, Pastel and Sapphire mink only exhibited from two to four bands. This to us indicated restricted polymorphism of the Muvi class I antigens for these mink. The restriction patterns varied from farm to farm. In the family material the Muvi antigens were found to segregate as expected. The French Wild mink were all naturally infected with Aleutian disease virus (ADV), a parvovirus, and their disease status classified as progressive or non-progressive. There were approximately 50% in each group. The mink were grouped into one of five class I Muvi profiles. When the profiles were compared to progressive versus non-progressive disease status, we found that mink with Muvi profile 4 and 5 almost exclusively (13 out of 15) were classified as having progressive Aleutian disease.

Spatial correlation between thyroid epithelial cells expressing class II MHC molecules and interferon-gamma-containing lymphocytes in human thyroid autoimmune disease

In this immunohistochemical study we addressed the question whether aberrant class II MHC expression by thyroid epithelial cells (thyrocytes) in established thyroid autoimmune disease is the result of release of interferon-gamma (IFN-gamma) by adjacent lymphocytes. Thyroids from eight cases of Hashimoto's thyroiditis, 13 cases of Graves' disease and 10 cases of focal thyroiditis were studied. Both thyrocytes expressing class II MHC and lymphocytes containing immunoreactive IFN-gamma were found in all 31 autoimmune thyroids. In a serial section study of these thyroids, IFN-gamma-expressing lymphocytes were found within 50 microns of class II MHC-positive thyrocytes in 89% of 282 randomly selected fields. Conversely, class II MHC-positive thyrocytes were found within 50 micron of aggregates of IFN-gamma-positive lymphocytes in 82% of 272 randomly selected fields. These findings support the view that in established thyroid autoimmune disease expression of class II MHC by thyrocytes is the result of local release of IFN-gamma.

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.

Evolution of the MHC: antigenicity and unusual tissue distribution of Xenopus (frog) class II molecules

Antibodies that recognize Xenopus class II molecules have been developed. Mouse monoclonal antibodies were prepared by immunizing BALB/c mice with frog MHC antigens that had been partially purified with alloantisera, and by immunizing mouse spleen cells in vitro with activated Xenopus T lymphocytes. In addition, five mouse monoclonal antibodies specific for human class II antigens were found to cross-react with Xenopus class II antigens. A.TH mice, which do not express E class II molecules, always produce immunoprecipitating antibodies reactive with frog class II molecules after immunization with frog lymphocytes; other mouse strains rarely produce such antibodies. Two of the monoclonal antibodies raised against frog class II molecules recognize the denatured class II beta chain on Western blots, and the other three appear to recognize only the class II heterodimeric complex. The antibodies display differential reactivity with the allelic class II products of Xenopus. The monoclonal antibodies react with all adult lymphocytes in the spleen and peripheral blood, T cells and B cells having equivalent levels of class II antigens per cell. Class II molecules are "differentiation antigens" on adult thymocytes as the expression is greatest on the mature medullary population. The number of class II molecules/lymphocyte increases after culturing in medium containing fetal bovine serum. Sequential immunoprecipitation and isoelectric focusing experiments have shown that cell surface class II molecules immunoprecipitated with the monoclonal antibodies are the same as those immunoprecipitated with the cross-reactive antiserum specific for DR antigens which was previously used to identify frog class II molecules.

The biosynthetic pathway of MHC class II but not class I molecules intersects the endocytic route

We studied the intracellular traffic and subcellular distribution of MHC class I and class II antigens in comparison with a recycling surface glycoprotein, the transferrin receptor (Tfr), in the human lymphoblastoid cell line JY. No internalization was detectable for class I molecules. Class II molecules were internalized but did not recycle. In contrast, Tfr was found to internalize and recycle. The biosynthetic pathway of class II molecules differ from that of class I molecules in that it shows a delay (1-3 hr) in transport from trans-Golgi to cell surface: here it intersects the endocytic route. Immunoelectron microscopy using anti-MHC antibodies revealed the existence of vesicular structures that were intensely labeled for class II molecules. It is proposed that at this site combination of class II molecules with processed antigen could occur.

The primary structure of a feline class I gene: striking similarity to HLA-A

The sequence of a feline class I pseudogene and its comparison with class I genes from other species is presented. The gene isolated is a pseudogene because of the presence of four stop codons and two frame shift mutations in the first- and second-domain encoding exons, as well as a mutation in a splice acceptor site in the third intron. By sequence comparison with the other class I sequences determined to date, the FLA pseudogene is most closely related to the HLA-A locus products (88% nucleotide identity.

Influenza virus changes cell-surface glycoproteins including major histocompatibility complex determinants on lymphocytes

The effect of influenza virus infection on the expression of major histocompatibility complex (MHC) antigens was investigated. Infection with influenza virus resulted in an increase of the binding of anti-MHC class I and class II antibodies to resting T cells. The binding of anti-MHC class II antibodies to activated T cells was increased approximately threefold. The binding of anti-MHC class I and class II antibodies to Epstein-Barr virus-transformed B cells appeared unaffected after influenza virus infection. Recombinant human interferon-alpha and/or -gamma added to T cells did not enhance the binding of anti-MHC antibodies. Biochemical analysis revealed no increase in the amount of class I and class II antigens as a consequence of viral infection, but a marked decrease in sialic acid content was found, most probably caused by the viral neuraminidase. Pulse-chase experiments suggest that the viral neuraminidase can catalyze the removal of sialic acids both en route to and at the cell surface. The absence of sialic acid residues can explain the increased binding of anti-MHC antibodies, because neuraminidase (clostridium perfringens) treatment of T and Epstein-Barr virus-transformed B cells resulted in a shift in both isoelectric point and antibody binding similar to that observed after influenza virus infection.

Isoelectric focusing of bovine major histocompatibility complex class I molecules

The products of the major histocompatibility complex (MHC) loci regulate an individual's immune response to pathogens. Cattle provide an important model to study the relationship between disease susceptibility and MHC haplotype since large half-sibling families are common. The definitive demonstration, however, of a firm relationship between MHC phenotype and disease susceptibility in cattle will require a precise definition of the bovine MHC allelic products. Available reagents for serological characterization of the bovine MHC gene products have not been adequate for these purposes. We have shown that existing mouse monoclonal antibodies and rabbit anti-human antisera precipitate bovine class I molecules, that these structures separate well by one-dimensional isoelectric focusing (1-D IEF), and that immunoprecipitation followed by 1-D IEF allows the detection of bovine class I MHC allelic products. Through this technique, we have identified previously undetected class I products. This approach will facilitate a detailed characterization of the bovine MHC class I gene products.

Isoelectric focusing of bovine major histocompatibility complex class II molecules

Serological approaches have been relatively unsuccessful in defining the allelic products of the bovine major histocompatibility (MHC) class II loci. We demonstrate that bovine class II allelic products can be characterized by precipitation with a polyclonal antiserum and separation using one-dimensional isoelectric focusing. Polymorphic beta chains were present in immunoprecipitates from both biosynthetically and surface-labeled lectin-stimulated bovine T cells. Precipitates from biosynthetically labeled but not surface-labeled T cells contained a basic invariant chain and a non-polymorphic structure. The non-polymorphic structure appears to be a beta chain. The polymorphic class II beta chain co-segregated with bovine MHC class I allelic products in a half-sibling family, providing evidence for linkage between bovine class I and class II loci. This approach to the biochemical analysis of the bovine class II structures should facilitate the investigation of the association between the bovine products and disease susceptibility.

Genetic characterization of FLA, the cat major histocompatibility complex

The major histocompatibility complex (MHC) of the domestic cat (termed FLA) has been refractile to genetic and serological definition largely because of repeated failure to detect cytotoxic antibodies in multiparous cats or to elicit antibody following allogeneic lymphocyte immunization. We have developed a protocol for producing cytotoxic alloantisera in the cat following rejection of multiple surgical skin grafts. Of 59 cats subjected to grafting, 13 produced lymphocytotoxic antisera which had varying specificities among a panel of outbred cat cells. A population cluster analysis of the 13 alloantisera permitted the identification of six clusters of overlapping FLA specificities. Serological analysis of cells from 12 cat kindreds led to the definition of 24 allogeneic haplotypes, which segregate as a single Mendelian complex. Feline FLA antisera were characterized as class I or class II specific by immunoprecipitation of FLA gene products on lymphocyte cell surfaces. Abundant antigenic polymorphisms for both class I and class II MHC determinants were discovered, a result consistent with precedence in other species and the common expectation of the adaptive value of MHC variation. Development of feline MHC typing reagents and the definition of haplotypes for the cat hold promise for experimental analysis of valuable feline models for virus-induced immune deficiencies.

A feline class II alpha gene with striking similarity to the HLA-DPA pseudogene

A genomic library was constructed from DNA of a domestic cat and screened with a human HLA-DR alpha probe at low stringency. Several positive clones were isolated, and the DNA sequence of one of these clones was determined. Comparison with class II alpha gene sequences from other species suggested that the feline gene is a DPA homologue (FLA-DPA) showing 84% similarity with HLA-DP alpha 1 in the exon encoding the second domain. The FLA-DPA gene that was isolated is a pseudogene, as two frame-shift mutations are present: one in the exon encoding the second domain, causing premature termination of translation, and one in the exon encoding the transmembrane region. The latter mutation and the further deletion of two codons in the transmembrane exon show a remarkable resemblance to the same exon of the human pseudogene, HLA-DPA2. Hence, both pseudogenes evolved from the same ancestral gene. The inactivation of this DPA gene could therefore have occurred prior to the major mammalian divergence.

Regulation of malignant B-cell proliferation by direct binding of anti-HLA class-II antibodies

A panel of five monoclonal antibodies (Mab) and a polyclonal antiserum directed against HLA class II were studied for their effect on growth of mature neoplastic B cells of prolymphocytic origin (B-PLL cells). The polyclonal antiserum and three out of five monoclonal antibodies were able to synergize with phorbol myristate acetate (PMA) to induce proliferation of B-PLL cells of one patient. Cross-blocking experiments showed that the proliferation-inducing Mab recognized closely related epitopes on HLA class-II molecules. The other two monoclonal antibodies recognized different epitopes on HLA class-II molecules and had no effect on proliferation of B-PLL cells. Proliferation induced by the combination of PMA and anti-HLA class-II Mab was inhibited by anti-CD18 (LFA-1) antibodies and was extremely dependent on cell density. This study indicates that certain HLA class II determinants on neoplastic B cells can transduce growth-promoting signals.

Recycling glycoproteins do not return to the cis-Golgi

Recycling of a number of glycoproteins along the site of action of mannosidase I (the distal endoplasmic reticulum/cis-Golgi) was followed in several different cell lines. Treatment of cells with 1-deoxymannojirimycin (dMM) produced high mannose oligosaccharides at positions otherwise occupied by complex-type oligosaccharides in these glycoproteins. Conversion of high-mannose-type oligosaccharides to complex oligosaccharides of proteins initially synthesized in the presence of dMM was used as a marker for recycling of glycoproteins along the site of action of dMM. In contrast to findings reported by Snider and Rogers (Snider, M. D., and O. C. Rogers. 1986. J. Cell Biol. 103:265-275), removal of dMM did not result in reconversion of high-mannose oligosaccharides to complex-type sugars, even after prolonged periods of culture. We conclude that surface glycoproteins do not recycle through the cis-medial Golgi elements.

The detection of conventional class I and class II I-E homologue major histocompatibility complex molecules on feline cells

The presence on feline cells of class I and class II I-E type major histocompatibility complex (MHC) homologues was demonstrated using cross-reacting monoclonal antibodies (mAb). The feline class I antigen homologues were detected with both immunofluorescent and biochemical techniques, using the anti-human class I mAb W6/32. The class I antigens were detected on in vitro cultured feline fibroblasts and lymphoid cells, but not on fresh lymphoid cells, apparently as a result of the association of bovine beta-2 microglobulin with feline class I heavy chains which generated the determinant(s) recognized by mAb W6/32. Class II I-E-like molecules could be detected with immunofluorescent techniques using the species cross-reactive anti-mouse I-E antibody 40D only when peripheral blood mononuclear cells were activated, for example, with the mitogens staphylococcus enterotoxin A or lipopolysaccharide. The predominant expression of I-A-like molecules by resting class II-positive feline cells could explain some of the functional difference we have seen in comparison with those of most other mammalian species.

Class II MHC expression in normal adrenal cortex and cortical cells in autoimmune Addison's disease

It has been proposed that aberrant expression of class II major histocompatibility complex (MHC) molecules by target cells may be an initiating factor in some forms of organ specific autoimmunity. This hypothesis was tested in relation to the autoimmune form of Addison's disease by studying autopsy adrenal glands from eight patients who had died of recent onset idiopathic Addison's disease. Using an immunohistochemical technique, class II MHC expression was found in a minority of adrenal cortical cells in the zona reticularis in 25 normal and four hyperplastic glands, while in Addison's disease almost all residual cortical cells expressed class II MHC. Three tuberculous adrenals showed increased staining of cortical cells around areas of chronic inflammation. It is concluded that since adrenal cortical cells of the normal gland express class II MHC, aberrant expression of this product cannot be invoked as an initiating mechanism in autoimmune adrenalitis. The increased cortical expression of class II MHC seen in idiopathic Addison's disease and tuberculosis may be due to local release of lymphokines by inflammatory cells.

Molecular characterization and genetic mapping of class I and class II MHC genes of the domestic cat

The major histocompatibility complex (MHC) of the domestic cat has been poorly characterized to date, primarily because of numerous difficulties in the preparation of allotypic sera. We present here a comparative analysis of class I and class II genes in domestic cat populations using molecular probes of the MHC from man and mouse. The cat possesses a minimum of 20 class I loci and 5 class II genes per haploid genome. Class I genes of the domestic cat expressed limited restriction fragment length polymorphism. The average percent difference of the size of DNA fragments between individual cats was 9.0%, a value five times lower than the value for mice, but comparable to the human DNA polymorphism level. Class I and class II genes were both genetically mapped to feline chromosome B2 using a panel of rodent x cat somatic cell hybrids. Since feline chromosome B2 is syntenically homologous to human chromosome 6 and mouse chromosome 17, these results affirm the linkage conservation of the MHC-containing linkage group in the three mammalian orders.

Aberrant expression of class II major histocompatibility complex molecules by B cells and hyperexpression of class I major histocompatibility complex molecules by insulin containing islets in type 1 (insulin-dependent) diabetes mellitus

Twenty-three patients with recent onset Type 1 (insulin-dependent) diabetes in whom residual insulin secreting B cells were present and 12 patients with disease of more prolonged duration (maximum 9 years), 8 of whom had residual B cells, were studied. Aberrant expression of Class II major histocompatibility complex molecules was demonstrated immunohistochemically on insulin secreting B cells in 21 out of 23 patients with recent onset disease and 6 of the patients with more prolonged disease. No such expression was seen on glucagon secreting A cells or somatostatin secreting D cells. Islets where there was marked hyperexpression of Class I major histocompatibility complex molecules on islet endocrine cells were seen in all cases in which residual B cells were present. Ninety-two per cent of insulin containing islets but only 1% of insulin deficient islets exhibited this phenomenon (p less than 0.001, Chi-squared test). There was evidence to suggest that both these abnormalities of major histocompatibility complex expression preceded insulitis within a given islet. They also appeared to be unique to Type 1 diabetes, being absent in pancreases of patients with Type 2 (non-insulin-dependent) diabetes, chronic pancreatitis, cystic fibrosis, graft-versus-host disease and Coxsackie B viral pancreatitis. The development of autoimmunity to B cells in Type 1 diabetes may be a "multistep" process in which abnormalities of major histocompatibility complex expression on islet endocrine cells are crucial events.