Isoforms of the CD79 signal transduction component of the macropod B-cell receptor

B cell responses and their concomitant signal transduction pathways are not well understood in marsupial mammals, despite the availability of gene expression data for key immunoglobulin genes and for elements of the CD79a/CD79b heterodimer signalling complex for two model marsupials. Broader studies of factors that influence B cell responses are still hampered by a lack of species-specific reagents and there are few reports of other factors that influence gene expression such as the potential for splice variants in BCR components, which may influence immune signalling pathways. In this study, we characterise CD79a and CD79b genes in the endangered macropod marsupial, Onychogalea fraenata (the bridled nailtail wallaby) and show that domains and residues important for the structural and functional integrity of both monomers are conserved in this species, consistent with results previously reported for the closely-related macropod, Macropus eugenii (the tammar wallaby). We extend this work to report the detection of splice variants for CD79a and CD79b in wallaby species; three CD79a isoforms and one CD79b isoform. Of these, two CD79a isoforms and the CD79b isoform have not been reported in any other mammalian species.

Immunohistochemical localization of T-lymphocyte subsets in the developing lymphoid tissues of the tammar wallaby (Macropus eugenii)

Research into marsupial adaptive immunity during ontogeny has been hampered by the lack of antibodies that react to marsupial immunological cell populations. In this study, newly synthesised polyclonal antibodies to the T cell marker, CD8, have been developed and used to investigate the ontogeny and distribution of this T cell population in the tammar wallaby. Immunohistochemical analysis indicated that the distribution of the CD8 lymphocytes in the lymphoid tissues of tammar neonates during the first 144 days of pouch life was similar to that of the eutherian mammals. However, CD8α(+) lymphocytes were observed in the intestines of tammar neonates prior to their first appearance in the cervical thymus, an observation that has not been found in eutherians. A dual labelling immunohistochemical approach was used for the indirect demonstration of CD4 and enabled the simultaneous detection in the tammar wallaby tissues of the two major T-lymphocyte populations, CD4 and CD8 that are associated with adaptive immunity. As in eutherian mammals, CD4(+) cells were the predominant T cell lymphocyte subset observed in the spleen while in the nodal tissues, an age-related decrease in the CD4(+)/CD8(+) ratio was noted. These antibodies provide a new immunological tool to study the role of T cell subsets in marsupial immunity and disease pathogenesis studies.

WFDC2 is differentially expressed in the mammary gland of the tammar wallaby and provides immune protection to the mammary gland and the developing pouch young

WAP four disulfide core domain 2 (WFDC2) is a four disulfide core (4-DSC) protein secreted in the milk of the tammar wallaby. It is comprised of two 4-DSC domains assigned domain III at the NH2-terminal end and domain II at the COOH-terminal end. The WFDC2 gene was expressed only during pregnancy, early lactation, towards the end of lactation and involution. The WFDC2 protein showed antibacterial activity against Staphylococcus aureus, Salmonella enterica and Pseudomonas aeruginosa and this activity resided with domain II. There was no antibacterial activity detected against Enterococcus faecalis. The observed expression pattern of tammar WFDC2 and its antibacterial activity suggests a role to either reduce mastitis in the mammary gland caused by S. aureus or to protect the gut of the young at a time when it is not immune-competent. The latter effect could be achieved without disturbing the balance of commensal gut flora such as E. faecalis.

The tammar wallaby major histocompatibility complex shows evidence of past genomic instability

BACKGROUND

The major histocompatibility complex (MHC) is a group of genes with a variety of roles in the innate and adaptive immune responses. MHC genes form a genetically linked cluster in eutherian mammals, an organization that is thought to confer functional and evolutionary advantages to the immune system. The tammar wallaby (Macropus eugenii), an Australian marsupial, provides a unique model for understanding MHC gene evolution, as many of its antigen presenting genes are not linked to the MHC, but are scattered around the genome.

RESULTS

Here we describe the 'core' tammar wallaby MHC region on chromosome 2q by ordering and sequencing 33 BAC clones, covering over 4.5 MB and containing 129 genes. When compared to the MHC region of the South American opossum, eutherian mammals and non-mammals, the wallaby MHC has a novel gene organization. The wallaby has undergone an expansion of MHC class II genes, which are separated into two clusters by the class III genes. The antigen processing genes have undergone duplication, resulting in two copies of TAP1 and three copies of TAP2. Notably, Kangaroo Endogenous Retroviral Elements are present within the region and may have contributed to the genomic instability.

CONCLUSIONS

The wallaby MHC has been extensively remodeled since the American and Australian marsupials last shared a common ancestor. The instability is characterized by the movement of antigen presenting genes away from the core MHC, most likely via the presence and activity of retroviral elements. We propose that the movement of class II genes away from the ancestral class II region has allowed this gene family to expand and diversify in the wallaby. The duplication of TAP genes in the wallaby MHC makes this species a unique model organism for studying the relationship between MHC gene organization and function.

Sub-cellular localisation of alkaline phosphatase activity in the cytoplasm of tammar wallaby (Macropus eugenii) neutrophils and eosinophils

Alkaline phosphatase (ALP) has been used in studies of neutrophil morphology and function as a marker for identifying different granule populations. In human neutrophils, ALP is found within secretory vesicles, a rapidly mobilisable vesicle population important for upregulating membrane receptors during early activation. Intra-cellular ALP activity in the heterophils of rabbits and guinea pigs, in contrast, is found only in secondary granules. The neutrophils and eosinophils of tammar wallabies (Macropus eugenii) have previously been reported to contain large amounts of ALP activity when stained using routine cytochemical techniques. To define the subcellular location of ALP in this species, cell suspensions were examined using cerium chloride cytochemistry and transmission electron microscopy (TEM). ALP was found in 2 distinct cytoplasmic compartments. One compartment displayed morphology consistent with a subpopulation of secondary granules while a second tubulo-vesicular population appeared similar to the secretory vesicles of human neutrophils. Thin tubular vesicles containing ALP were also identified within the cytoplasm of tammar wallaby eosinophils. Large numbers of ALP-containing vesicles have not been recognised previously in eosinophils and this may represent a novel cytoplasmic compartment. In both cell types, ALP-containing structures showed alteration in morphology following stimulation with N-formyl-Met-Leu-Phe (fMLP) and PMA.

A proteomic approach to analysis of antimicrobial activity in marsupial pouch secretions

We have documented the antimicrobial activity of pouch secretions of the tammar wallaby, Macropus eugenii, over the period leading up to birth and after birth of the young animal. This activity was greatest against the Gram-negative Escherichia coli and highest at the time of birth. Fractionation of the pouch secretions showed that activity at different times over the reproductive periods was associated with different molecular-weight (MW) components, with compounds in the range up to 50 kDa active immediately prior to and at the time of birth. Proteomic analysis using 1 and 2DE PAGE and LC-MS/MS identified the major components of the pouch secretions at these times, at a range of pI's and MWs. The majority of high-confidence identifications, at a wide range of pI's and MW, were beta-lactoglobulin, a known component of marsupial milk. We subsequently conducted a proteomic analysis of mammary gland secretions and digest products from the gut of the young animal, using 2DE PAGE and MALDI MS/MS, to confirm its source and compare it with the observed MW and pI's of beta-lactoglobulin. Although we did not directly identify an effector molecule responsible for antimicrobial activity, these results lead us to propose that beta-lactoglobulin plays a role in the protection of the young marsupial, a role previously thought to be primarily due to specific secretions from the epithelial surface of the pouch.

Comparative modeling of marsupial MHC class I molecules identifies structural polymorphisms affecting functional motifs

Major histocompatibility complex (MHC) class I molecules are transmembrane glycoproteins that present antigenic peptides to CD8+ T cells and are subsequently important for the initiation of an immune response. In this study novel MHC class I sequences from the tammar wallaby (Macropus eugenii) have been characterized. Analysis and comparative modeling of these and existing marsupial molecules reveals potential functional polymorphisms within peptide-binding grooves, MHC assembly motifs and the T cell receptor recognition interface. In addition, we show that a previously identified marsupial-specific insertion is within a region, which is known as a putative NK cell receptor (Ly49A) binding site in the mouse, suggesting that this site may be functionally active in marsupials. Further, the analysis highlighted differences in structural and sequence based grouping of marsupial MHC class I molecules.

Characterization and expression of Peroxiredoxin 1 in the neonatal tammar wallaby (Macropus eugenii)

Peroxiredoxin 1 (PRDX1) is a ubiquitously expressed antioxidant with vital roles in basal metabolic functions. In addition PRDX1 is involved in cell differentiation and proliferation, apoptosis and innate immunity. In this study, we have characterized PRDX1 from the tammar wallaby (Macropus eugenii). Tammar PRDX1 has high conservation of functional residues and motifs, and demonstrates a close homology with eutherian and vertebrate orthologues. Stimulation of adult tammar leukocytes with lipopolysaccharide and lipoteichoic acid suggests a role for PRDX1 in innate immune defences. PRDX1 expression in the organs of tammar pouch young was mildly elevated early in life possibly reflecting its role in basal metabolic processes. Later increases in PRDX1 expression correlated with functional maturation of several immune organs or with preparation for increased oxidative stress of emergence. The findings of the study are reflections of the complex integrated roles that PRDX1 has in regulation of oxidative stress, apoptosis, cell differentiation and proliferation, and innate immunity.

In search of neutrophil granule proteins of the tammar wallaby (Macropus eugenii)

Two approaches have been used to isolate and identify proteins of the granules of neutrophils of the tammar wallaby, Macropus eugenii. Stimulation with PMA, Ionomycin and calcium resulted in exocytosis of neutrophil granules as demonstrated with electron microscopy. However proteomic analysis using two dimensional gel electrophoresis, in-gel trypsin digestion followed by nano liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) failed to identify any anticipated granule proteins in the reaction supernatants. Subsequent use of differential centrifugation and lysis followed by the application of the same proteomic analysis approach resulted in the isolation and confident identification of 39 proteins, many of which are known to be present in the granules of neutrophils of eutherian mammals or play a role in degranulation. These proteins notably consisted of the known antimicrobials, myeloperoxidase (MPO), serine proteinase, dermcidin, lysozyme and alkaline phosphatase. A number of important known antimicrobials, however, were not detected and these include defensins and cathelicidins. This is the first report of the neutrophil granule proteins of any marsupial and complements previous reports on the cytosolic proteins.

Analysis of the expression of immunoglobulins throughout lactation suggests two periods of immune transfer in the tammar wallaby (Macropus eugenii)

Marsupial young are born in an under-developed state without mature immune responses. Prior to the maturation of an immune system, marsupial young are heavily reliant upon immune factors secreted in the milk to defend them against potential microbial pathogens in the environment. In this study, we identified and characterized the immunoglobulin heavy chain constant regions, light chains, polymeric Ig receptor (pIgR), J chain, neonatal Fc receptor (alpha chain) (FcRn) and the chemokine CCL28 from the model marsupial species, the tammar wallaby (Macropus eugenii). Low levels of conservation were seen in motifs in C alpha and C gamma associated with receptor binding and or transcytosis, and this may have potential implications for functionality. We evaluated the expression of immunoglobulin genes in the tammar mammary gland throughout lactation and found that two periods of increased expression of immunoglobulin genes occur. These two periods coincide with the birth of the young, and with its first emergence from the pouch. This increased expression may represent a strategy for maternal immunological protection of the pouch young.

Serologic responses of Barbary sheep (Ammotragus lervia), Indian antelope (Antilope cervicapra), wallaroos (Macropus robustus), and chimpanzees (Pan troglodytes) to an inactivated encephalomyocarditis virus vaccine

Encephalomyocarditis virus (EMCV) is a picornavirus with a worldwide distribution, capable of infecting a wide range of species. Episodes of EMCV-associated mortality have been reported in zoos and national parks around the world, including sporadic cases at Taronga Zoo, Sydney. An inactivated EMCV vaccine was evaluated by inoculating Barbary sheep (Ammotragus lervia), Indian antelope (Antilope cervicapra), Eastern wallaroos (Macropus robustus), and chimpanzees (Pan troglodytes). A proportion of the vaccinated ungulates were administered a second vaccination 4 wk after the initial dose. Neutralizing antibody titers were monitored for a period of 12 mo. One month after vaccination, all vaccinated groups had developed significant antibody titers that persisted for at least 6 mo. Animals receiving two doses of vaccine had higher titers 3, 6, and 12 mo after the initial vaccination compared with animals receiving a single vaccine dose.

Culture and Stimulation of Tammar Wallaby Lymphocytes

We describe the culture and stimulation of lymphocytes from the model marsupial, the tammar wallaby (Macropus eugenii). We also describe the capacity of tammar wallaby lymphocytes isolated from blood, spleen and lymph nodes to produce soluble immunomodulatory factors. Culture conditions were optimized for mitogen-driven stimulation using the plant lectin phytohaemagglutinin (PHA). Products secreted by stimulated cells were harvested and crudely fractionated before they were added back to freshly isolated lymphocytes. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) assay, both stimulatory and inhibitory bioactive factors were detected in serum-free supernatants harvested from mitogen-treated peripheral blood mononuclear cells. This paper describes the capacity of leukocytes of the tammar wallaby to respond to mitogenic stimulation and to produce soluble, low-molecular-weight bioactive molecules that possess cytokine-like activity.

Immunisation of the male tammar wallaby (Macropus eugenii) with spermatozoa elicits epididymal antigen-specific antibody secretion and compromised fertilisation rate

Immunocontraception has been proposed as an effective and humane means of controlling overabundant kangaroo populations in Australia. We have examined the feasibility of using a sperm-based vaccine for this purpose using a model macropod species, the tammar wallaby (Macropus eugenii). This study has demonstrated immunocontraception in a marsupial species following immunisation of males with homologous spermatozoa. Serum anti-sperm IgG titres were associated with a significant reduction in fertilisation rates following mating with superovulated female wallabies. Antigen-specific IgG penetrated the reproductive tract at the rete testis and bound spermatozoa in vivo. IgG was detected bound to the acrosome and midpiece regions of both epididymal and ejaculated spermatozoa. The absence of adverse testicular pathology and sperm movement effects suggests that contraception may have been achieved by antibody-mediated blocking of sperm surface antigens essential for fertilisation. This study demonstrates that a contraceptive vaccine targeting sperm antigens has potential for fertility control in male macropods.

Isolation of major histocompatibility complex Class I genes from the tammar wallaby (Macropus eugenii)

The major histocompatibility complex (MHC) plays an essential role in the adaptive immune system of vertebrates through antigen recognition. Although MHC genes are found in all vertebrates, the MHC region is dynamic and has changed throughout vertebrate evolution, making it an important tool for comparative genomics. Marsupials occupy an important position in mammalian phylogeny, yet the MHC of few marsupials has been studied in detail. We report the isolation and analysis of expressed MHC Class I genes from the tammar wallaby, a model marsupial used extensively for the study of mammalian reproduction, genetics, and immunology. We determined that there are at least 11 Class I loci in the tammar genome and isolated six expressed Class I sequences from spleen and testes cDNA libraries, representing at least four loci. Two of the Class I sequences contain substitutions at sites known to be important for antigen binding, perhaps impacting their ability to bind peptides, or the types of peptide to which they bind. Phylogenetic analysis of tammar wallaby Class I sequences and other mammalian Class I sequences suggests that some tammar wallaby and red-necked wallaby loci evolved from common ancestral genes.

Analysis of the genomic region containing the tammar wallaby (Macropus eugenii) orthologues of MHC class III genes

Major histocompatibility complex (MHC) molecules are central to development and regulation of the immune system in all jawed vertebrates. MHC class III cytokine genes from the tumor necrosis factor core family, including tumor necrosis factor (TNF) and lymphotoxin alpha and beta (LTA, LTB), are well studied in human and mouse. Orthologues have been identified in several other eutherian species and the cDNA sequences have been reported for a model marsupial, the tammar wallaby. Comparative genomics can help to determine gene function, to understand the evolution of a gene or gene family, and to identify potential regulatory regions. We therefore cloned the genomic region containing the tammar LTB, TNF, and LTA orthologues by "genome walking", using primers designed from known tammar sequences and regions conserved in other species. We isolated two tammar BAC clones containing all three genes. These tammar genes show similar intergenic distances and the same transcriptional orientation as in human and mouse. Gene structures and sequences are also very conserved. By comparing the tammar, human and mouse genomic sequences we were able to identify candidate regulatory regions for these genes in mammals. Full length sequencing of BACs containing the three genes has been partially completed, and reveals the presence of a number of other tammar MHC III orthologues in this region.

Culture and characterisation of peripheral blood monocytes and monocyte-derived adherent cells of the tammar wallaby, Macropus eugenii

Monocytes, monocyte-derived adherent cells and dendritic cells all play a role in cellular immunity. In this study, we describe the isolation of monocyte-derived adherent cells and dendritic cells from a model marsupial, the tammar wallaby, Macropus eugenii, and report that in vitro, these cells appear morphologically similar to these cells found in other mammals. The successful culture of marsupial monocyte and dendritic cells was undertaken in serum-free medium which contained lymphocyte conditioned medium as an absolute requirement. This supports the view that similar to cultured dendritic cells from other species reported to date, specific growth factors are required to promote the maturation and differentiation of these cells.

An immunomodulator used to protect young in the pouch of the Tammar wallaby, Macropus eugenii

Eugenin [pGluGlnAspTyr(SO(3))ValPheMetHisProPhe-NH(2)] has been isolated from the pouches of female Tammar wallabies (Macropus eugenii) carrying young in the early lactation period. The sequence of eugenin has been determined using a combination of positive and negative ion electrospray mass spectrometry. This compound bears some structural resemblance to the mammalian neuropeptide cholecystokinin 8 [AspTyr(SO(3))MetGlyTrpMetAspPhe-NH(2)] and to the amphibian caerulein peptides [caerulein: pGluGlnAspTyr(SO(3))ThrGlyTrpMetAspPhe-NH(2)]. Eugenin has been synthesized by a route which causes only minor hydrolysis of the sulfate group when the peptide is removed from the resin support. Biological activity tests with eugenin indicate that it contracts smooth muscle at a concentration of 10(-9) M, and enhances the proliferation of splenocytes at 10(-7) M, probably via activation of CCK(2) receptors. The activity of eugenin on splenocytes suggests that it is an immunomodulator peptide which plays a role in the protection of pouch young.

Interferon alpha/beta genes from a marsupial, Macropus eugenii

This paper describes the cloning of full length marsupial type I interferon (IFN) genes and their flanking regions using a genome walking approach and PCR primers based on previously isolated partial DNA sequences. We confirm that the two major classes of Tammar Wallaby type I IFN genes are homologous with the eutherian IFN-alpha and IFN-beta gene families. The wallaby IFN genes share a number of conserved features with their eutherian counterparts, including codons for cysteines at equivalent positions, implying similar secondary structures for the encoded proteins, and promoter regions with conserved putative regulatory motifs. Moreover, the wallaby genes have AT-rich elements in their flanking sequence corresponding to the mRNA 3'-untranslated regions, also implying that, as in eutherian mammals, rapid mRNA degradation plays a role in regulating expression of these genes. The complex nature of the type I IFN gene families in viviparous mammals (eutherians and marsupials) may reflect their recruitment into nonimmunological processes and this concept is discussed.

Porcine zonae pellucidae immunization of tammar wallabies (Macropus eugenii): fertility and immune responses

This study looked at the feasibility of targeting the zona pellucida for a contraceptive vaccine as a possible alternative method of control for overabundant macropods. Tammar wallabies, as a model for other macropods, were immunized with porcine zonae pellucidae (PZP) and were found to achieve significant concentrations of antibody to PZP in sera and reproductive tract fluids. Wallabies immunized with PZP exhibited lower ovarian weight with reduced numbers of antral follicles when compared with control animals. Wallabies were placed in a natural mating trial followed by an artificial insemination trial. None of the PZP-immunized wallabies produced offspring in the natural mating trial compared with 67% of control animals. To further assess fertility, a sub-sample of the wallabies were superovulated and artificially inseminated. This resulted in all control wallabies producing fertilized ova and all PZP-immunized wallabies failing to ovulate. These results suggest that immunocontraception based on targeting antigens of the zona pellucida may be an effective strategy for fertility reduction in macropods.

The detection of mature T- and B-cells during development of the lymphoid tissues of the tammar wallaby (Macropus eugenii)

The distribution of T- and B-cells in the developing lymphoid and immunohaematopoietic tissues of the tammar wallaby were investigated using antibodies to the mature cell surface markers, CD3, CD5 and CD79b. In the thymus, CD3- and CD5-positive T-cells were first observed at day 12 postpartum whilst rare B-cells were first detected at day 23. Both T- and B-lymphocytes were first stained on day 21 postpartum in the spleen and day 24 in lymph nodes. In one sample from a 7-day-old animal, rare CD79b-positive (CD79b+) lymphocytes were observed in the gut-associated lymphoid tissues. However, CD3+ cells were not apparent until day 12 and CD5+ cells were not detected until day 74 postpartum. No lymphocytes were detected in liver or bone marrow samples and no bronchus-associated lymphoid tissues were observed. The pattern of development and the distribution of T- and B-cells in the lymphoid and immunohaematopoietic tissues were similar to those observed in eutherian mammals and in limited studies of other metatherians. However, the detection of apparently mature T- and B-cells in the thymus and gut-associated lymphoid tissues (GALT) at the same postnatal age highlights the need for a more substantial study of the development of GALT. This is, at present, limited by availability of marsupial-specific antibodies.

Histological and immunohistological investigation of the lymphoid tissue in normal and mycobacteria-affected specimens of the Rufous Hare-wallaby (Lagorchestes hirsutus)

The histology of the spleen, lymph nodes, Gut-associated lymphoid tissue (GALT) and Bronchus-associated lymphoid tissue (BALT) are described for samples collected opportunistically from healthy and mycobacteria-affected specimens of the endangered marsupial Lagorchestes hirsutus, the Rufous Hare-wallaby. The structural elements, organization and distribution of T and B lymphocytes determined by immunohistological techniques using species cross-reactive antibodies in the lymph nodes, spleen and GALT of this species demonstrated lymphoid cell distributions that were consistent with other marsupial and eutherian mammals. The tissues of animals identified as acid-fast positive displayed immunopathology consistent with the responses to intracellular bacteria displayed in some eutherian mammals and included the presence of focal lesions, giant cells in the lung and lymphoid aggregations situated adjacent to blood and airway vessels. This is the first study to describe the lymphoid tissue of this rare macropod species and the first to document the tissue bed response to mycobacteria.

Immune response of the tammar wallaby (Macropus eugenii) to sperm antigens

In the present study, male and female tammar wallabies were immunised with whole tammar wallaby sperm in adjuvant. An assay for sperm antibodies using a live sperm ELISA has been developed to detect sperm surface antigens and used to validate an assay using a 3-[(3-cholamidopropyl) dimethylammonio]-1 propanesulfonate (CHAPS) membrane extract of whole tammar wallaby sperm. The tests were used to monitor the immune response to whole sperm in both male and female tammar wallabies. Antisera with a limited array of specificities were generated, with those locating to the midpiece region of the sperm appearing the most likely candidates for targets for fertility perturbation based on immunofluorescence of fixed and non-fixed sperm. These systemically generated antibodies were demonstrated to have access to both the female and male tammar reproductive tracts and were found on ejaculated sperm and antibodies from female sera and follicular fluid-labelled fresh ejaculated sperm from non-immunised males. Preliminary sequencing of these proteins has identified some possibilities for further investigation.

Immunohistochemistry of the lymphoid tissues of the tammar wallaby, Macropus eugenii

The lymphoid tissues of the metatherian mammal, the adult tammar wallaby, Macropus eugenii, were investigated using immunohistochemical techniques. Five cross-reactive antibodies previously shown to recognize surface markers in marsupial tissues and five previously untested antibodies were used. The distribution of T-cells in the tissue beds of spleen, lymph node, thymus, gut-associated lymphoid tissue (GALT) and bronchus-associated lymphoid tissue (BALT) was documented using antibodies to CD3 and CD5. Similarly, B-cells were identified in the same tissues using anti-CD79b. Antibodies to CD8, CD31, CD79a and CD68 failed to recognize cells in these tissue beds. In general the pattern of cellular distribution identified using these antibodies was similar to that observed in other marsupial and eutherian lymphoid tissues. This study provides further information on the commonality of lymphoid tissue structure in the two major groups of extant mammals, metatherians and eutherians.

Histology and immunohistochemistry of the gut-associated lymphoid tissue of the eastern grey kangaroo, Macropus giganteus

Mesenteric lymph nodes and gut-associated lymphoid tissue (GALT) from juvenile eastern grey kangaroos were investigated. The mesenteric nodes had a similar structure to that described for eutherian mammals. They contained distinct regions of medulla and cortex, with prominent follicles and germinal centres. Gut associated lymphoid tissue consisted of areas of submucosal follicles. These varied from areas of densely packed lymphocytes with darkly staining, prominent coronas to areas with no defined follicles. The distribution of T cells in these tissues was documented by use of species-crossreactive antibodies to the surface markers CD3 and CD5; B cells were identified by antibodies to CD79b. Within the lymph nodes T cells were located mainly in the paracortex and cortex, with limited numbers observed in the follicles; B cells were located on the marginal zone of the follicles. In GALT, T cells were located in the peripheral regions of the germinal centres of secondary follicles, while B cells were abundant in primary follicles. These observations are consistent with those made in a range of other marsupials (metatherian) and eutherian mammals and are indicative of the capacity to respond to antigens entering via the mouth.

Molecular characterisation of the tammar wallaby (Macropus eugenii) CD3 epsilon chain cDNA

The cDNA encoding the epsilon chain of the tammar wallaby CD3 complex (CD3epsilon) was isolated by PCR. This is the first CD3 component to be cloned in a marsupial. The tammar wallaby cDNA coding region was 61.7 and 63.0% identical to the human and mouse cDNA coding sequences, respectively. Similarly, the predicted amino acid sequence was 56.5 and 52.9% identical to the human and mouse sequences. When compared with other known CD3epsilon peptide sequences, the most conserved region of the tammar wallaby CD3epsilon chain peptide was the cytoplasmic domain and the least conserved was the extracellular portion. Phylogenetic reconstruction based on the deduced amino acid sequence placed the tammar wallaby sequence in its expected position outside of all the eutherian mammals.

Characterisation of fibrous sheath and midpiece fibre network polypeptides of marsupial spermatozoa with a monoclonal antibody

In this study cytoskeletal antigens common to brushtail possum and tammar wallaby spermatozoa were characterised using a monoclonal antibody (PSA-10). Using indirect immunofluorescence, the PSA-10 antibody detected antigens predominantly associated with the midpiece and principal piece of mature, permeabilised marsupial spermatozoa. The principal piece determinant, shared by a variety of other species, was found to arise in the marsupial testis. Midpiece localisation of the PSA-10 epitope was detected only in marsupial spermatozoa and shown to arise in the epididymis. Immunogold labelling demonstrated that the PSA-10 antigens were predominantly associated with the fibrous sheath and midpiece fibre network of both possum and wallaby spermatozoa. Western blotting suggested that two major possum and wallaby sperm polypeptides of 158 and 182 kDa were associated with the midpiece fibre network, a cytoskeletal structure unique to marsupial spermatozoa. A 32 kDa polypeptide was associated with the principal piece fibre network and/or fibrous sheath. The finding that these marsupial sperm cytoskeletal proteins share a common linear epitope suggests that they share some sequence similarity. The midpiece fibre network of marsupial sperm, like the fibrous sheath, has been proposed to have a structural role in providing passive stiffening for the flagellum (Harding et al., 1975, 1979; Olsen, 1975). The PSA-10 monoclonal antibody may provide a tool for comparative studies of mammalian sperm cytoskeletal proteins, particularly the marsupial midpiece fibre network. It may also allow the formation of this unique marsupial cytoskeletal structure, and its fate during the fertilisation process, to be followed by immunological means.

Sequence convergence in the peptide-binding region of primate and rodent MHC class Ib molecules

In addition to the universally expressed and highly polymorphic class Ia genes, the major histocompatibility complex (MHC) of placental mammals includes class Ib genes that are characterized by restricted expression and low levels of sequence polymorphism. The functional importance of class Ib genes as well as their actual function has long been controversial. Phylogenetic analyses have suggested that there are no orthologous relationships among class Ib loci of mammals belonging to different orders, suggesting that these loci have evolved independently since the placental mammals diverged. Here, we present evidence of convergent evolution at the molecular sequence level in the putative peptide-binding regions (PBRs) of human and mouse class Ib genes. So far, there are few if any convincing examples of convergent evolution at the amino acid sequence level, and such evolution is believed to be likely to occur only as a result of strong positive selection. Because the present case involves the functionally important PBR and because the primate and rodent molecules are known to bind similar peptides, this study represents both a convincing case of molecular-level convergence and evidence that MHC class Ib molecules, although not orthologous, may evolve similar functions convergently.

Development of the lymphoid tissues of the tammar wallaby Macropus eugenii

A study has been made of the development of four lymphoid tissues from birth to maturity in the tammar wallaby Macropus eugenii--the cervical and thoracic thymus, lymph nodes and gut-associated lymphoid tissue (GALT). The development of these tissues in the tammar wallaby is similar to that in two other marsupials, the quokka Setonix brachyurus and the Virginian opossum Didelphis virginiana. Lymphocytes were first detected in the cervical thymus of the tammar at Day 2 post partum and in the thoracic thymus at Day 6. They were subsequently detected in lymph nodes at Day 4 and in the spleen by Day 12 but were not apparent in the GALT until around Day 90 post partum. By Day 21, the cervical thymus had developed distinct areas of cortex and medulla and Hassall's corpuscles were apparent. The maturation of other tissues followed with Hassall's corpuscles in the thoracic thymus by Day 30 and nodules and germinal centres in the lymph nodes by Day 90. Measurement of immunoglobulin G concentrations in the serum of young animals indicated a rise in titre around Day 90 post partum, correlating with the apparent maturation of the lymphoid tissues.

Class I major histocompatibility complex genes of the red-necked Wallaby, Macropus rufogriseus

Marsupials are one of three main evolutionary lineages in mammals, the other two being the monotremes and the placental mammals. The marsupial and the placental lineages separated between 120 and 156 million years ago. In this communication, we provide the first molecular description of class I major histocompatibility complex (Mhc) genes in a representative of the marsupial lineage, the red-necked wallaby, Macropus rufogriseus. Three different, nearly full-length class I Mhc sequences were identified in the cDNA library prepared from spleen mRNA of a single wallaby. The three sequences identify at least two loci. Under the assumption that two of the identified sequences are alleles, we designate the three wallaby genes Maru-Mhc-UA*01, Maru-Mhc-UA*02, and Maru-Mhc-UB*01. The three Maru sequences share several codon deletions and insertions not found in the class I genes of placental mammals. Comparisons of genetic distances among the known class I genes suggest that the Maru genes arose from one ancestral element, whereas the class I genes of the placental mammals arose from another, different ancestral element. The absence of an identifiable defect in the three Maru sequences suggests that the genes from which they were derived are functional. Hence, as in placental mammals, there appear to be two functional class I Mhc loci in the marsupials as well.

Immunoglobulin G levels in fetal and newborn tammar wallabies (Macropus eugenii)

Immunoglobulin G (IgG) was measured in fetal, neonatal and colostral samples from the tammar wallaby (Macropus eugenii) in order to study the possibility of passively acquired immunity. Samples were obtained from young at a known stage of gestation and at known times (to the minute) after birth. IgG was present (in increasing levels of concentration) in fetal serum, neonatal serum and colostrum. Since the fetus and neonate are probably unable to make immunoglobulin (Ig), it is hypothesized that transplacental and trans-gut transmission takes place from mother to offspring. The vascular yolk sac placenta has a high concentration of IgG, and is the most likely route of transmission from mother to young. Some observations were made of IgA which was found only in colostrum. No Ig of either kind was found in yolk sac fluid.

Lack of evidence for complement-dependent cytotoxic antibodies to fetal paternally derived antigens in the marsupial Macropus eugenii (tammar wallaby)

A total of 241 serum samples from 145 parous tammar wallabies (Macropus eugenii) were screened for presence of antibodies to paternally derived antigens of the fetus. These samples were taken at different stages in late pregnancy after placental contact was intimate and after birth. Complement-dependent cytotoxicity tests were unable to detect any specific antibodies. It is concluded that the yolk sac placenta of M. eugenii does not allow intimate enough contact between fetal tissues and the maternal circulation to induce formation of cytotoxic antibodies by its mother. This is in contrast to eutherian mammals, in which such production of cytotoxic antibodies occurs frequently as a result of pregnancy. Together with other data it is suggested that the short implantation period in M. eugenii, which is common to all marsupials, has probably not evolved to prevent maternal immune attack upon the conceptus.

Vaccination against lumpy jaw and measurement of antibody response in wallabies (Macropus eugenii)

Successful protection against lumpy jaw disease in a colony of captive wallabies (Macropus eugenii) was induced by vaccination with a commercial ovine footrot vaccine. No mortalities attributable to lumpy jaw were observed in 69 vaccinated animals while six of 42 unvaccinated control wallabies died of the disease. Vaccinated animals exhibited significant increases in antibody titres to Bacteroides nodosus after the first and second doses of vaccine. Titres were measured by an enzyme-linked immunosorbent assay.

In vitro antibody-mediated macrophage activity on Breinlia macropi microfilariae. II. Ultrastructural and video recording investigations of adherence and cytotoxicity

Video recordings and ultrastructural studies have revealed an intricate sequence of antibody-mediated cytotoxic activity by quokka peritoneal macrophages on Breinlia macropi microfilariae. The microfilaricidal activity was effected by at least two types of macrophages measuring 17 micrometers and 8 micrometers in diameter respectively. The relatively large macrophages were responsible for trapping, encircling and eventually degrading the highly motile microfilariae in a sequence of events in which the participating macrophages may interdigitate. The smaller macrophages adhered transiently to a number of adjacent sites on the surface of a trapped microfilaria, resulting in a series of damaged spots. This activity of the small macrophages was interpreted as responsible for killing the microfilaria. Thus the microfilaricidal activity was interpreted to be accomplished by the co-operative functions of the relatively large and small macrophages.

Active anti-paternal immunization does not affect the success of marsupial pregnancy

Active anti-paternal immunization does not compromise pregnancy in eutherian mammals. However, in an earlier study in a marsupial, grafting with paternal skin appeared to have resulted in transient infertility. In the present study, by critically monitoring the breeding efficiency of tammar wallabies sensitized against their mate's transplantation antigens, we aimed to resolve the question of immunologically mediated infertility in marsupials. Eight experimental females received two full-thickness skin grafts from their prospective mate and eight controls grafts of their own skin. The experimental group were monitored for 30 reproductive cycles and produced 24 pouch young (PY), whereas the control animals produced 28 young from 33 cycles. Five of the 11 apparently non-fertile cycles were judged to be normal pregnancies where the young had failed to reach the pouch (cycle length less than 28 days; rapid plasma progesterone decline coincident with oestrus). True infertility was thus limited and, although occurring mainly in the male-skin grafted group (5 cycles), this was not significantly different (chi 2, P greater than 0.5) from the controls (1 cycle) and represented the effect of one very poor breeder. We conclude that allogeneic pregnancy in marsupials is not compromised by active anti-paternal immunization. Infertility observed here, and in the earlier study, reflected disturbance of breeding owing to handling of the animals or the poor reproductive efficiency of individual animals in small experimental groups.

Immunology of pouch young marsupials. I. Levels of immunoglobulin transferrin and albumin in the blood and milk of euros and wallaroos (hill kangaroos: Macropus robustus, marsupialia)

The concentration of total protein, albumin, transferrin, and immunoglobulin G of adult serum, pouch young serum, milk whey and colostrum has been estimated in three species of kangaroos, Macropus robustus, Macropus rufus (= Megaleia rufa) and Macropus giganteus. No study of this kind has previously been published for any marsupial species. The three individual proteins were antigenically identical in all four kinds of fluid. Colostrum and milk whey are relatively enriched in transferrin but have low levels of immunoglobulin G. Serum concentrations of total protein, albumin and transferrin rise steadily throughout pouch life and attain adult values when the young finally leaves the pouch. Serum concentrations of immunoglobulin G are very low for the first 90-100 days of pouch life, being approximately half of those in milk whey for this period. After this the level rises rapidly and also reaches adult values when the young leaves the pouch. We suggest that in the first 90-100 days the pouch young is largely protected humorally by passive immunity acquired from the mother, and after this it increasingly makes its own responses.

A serological survey of Australian wildlife for antibodies to Leptospires of the Hebdomadis serogroup

A serological survey for antibodies to Leptospira interrograns serovar hardjo was conducted on 574 serum samples from 10 native and 4 introduced wildlife species in south-eastern Australia. The microscopic agglutination (MA) test was used, and titres to hardjo antigen were detected in 33.5% of 352 brushtailed possums (Trichosurus vulpecula) sampled in several areas of Victoria. Prevalence of reactors ranged from 14 to 66% in 4 populations examined intensively. Serovar balcanica was isolated from possums with hardjo antibodies from two different areas. Of 20 wombats Vombatus ursinus) examined in Victoria, antibodies to hardjo were found in sera from 4 and titres to Pyrogenes and Pomona serogroups were detected in another. Hardjo antibodies were demonstrated in sera from 13 of 19 rusa deer (Cervus timorensis). Negative MA test results to hardjo antigens were recorded in 55 mountain possums (T. caninus), 63 macropods (Macropus spp.), 17 water rats (Hydrmys chrysogaster), 39 fallow deer (Dama dama), 2 hog deer (Axis porcinus) and 2 water buffalo (Bubalus bubalus). No MA antibodies to any of 16 leptospiral serogroups were detected in 17 water rats tested. Kidneys were examined from 330 of these animals and focal interstitial nephritis suggestive of leptospirosis was found in kidneys of 63 of 169 T. vulpecula, 3 of 55 T. caninus, 12 of 18 V. ursinus, 6 of 22 Macropus spp., 9 of 16 H. chrysogaster, 5 of 11 C. timorensis and 3 of 39 D. dama. A statistical association between focal interstitial nephritis and MA antibodies to hardjo was found in T. vulpecula.

Immunological aspects of gestation in the tammar wallaby, Macropus eugenii

Sensitization to male histocompatibility antigens and repeated pregnancy to the same male were found to have little effect on fertility or length of gestation in the tammar wallaby, M. eugenii. However, in some sensitized females a long interval occurred between removal of pouch young and the next birth. In addition to studies on fertility, the immunological response of female tammars to their mate has been examined by one-way mixed leucocyte culture (MLC) carried out at the beginning and end of one breeding season. In virgin females, examined at the beginning of the breeding season, the MLC response to the prospective mate peaked on day 6. In contrast, by the end of the season, MLC responses were much lower and peaked earlier, on day 3 to day 5.