Humoral immune response in a marsupial Monodelphis domestica: anti-isotypic and anti-idiotypic responses detected by species-specific monoclonal anti-immunoglobulin reagents

Immunogenetics of marsupial B-cells

Marsupials and eutherians are mammals that differ in their physiological traits, predominately their reproductive and developmental strategies; eutherians give birth to well-developed young, while marsupials are born highly altricial after a much shorter gestation. These developmental traits also result in differences in the development of the immune system of eutherian and marsupial species. In eutherians, B-cells are the key to humoral immunity as they are found in multiple lymphoid organs and have the unique ability to mediate the production of antigen-specific antibodies in the presence of extracellular pathogens. The development of B-cells in marsupials has been reported and hypothesised to be similar to that of eutherians, except that haematopoiesis occurs in the liver, postpartum, until the bone marrow fully matures. In eutherians, specific genes are linked to specific stages in B-cell development, maturation, and differentiation processes, and have been identified including immunoglobulins (heavy and light chains), cluster of differentiation markers (CD10, 19, 34 and CD79α/β), signal transduction molecules (BTK, Lyn and Syk) and transcriptional regulators (EBF1, E2A, and Pax5). This review aims to discuss the known similarities and differences between marsupial and eutherian B-cells, in regards to their genetic presence, homology, and developmental stages, as well as to highlight the areas requiring further investigation. By enhancing our understanding of the genes that are involved with B-cells in the marsupial lineage, it will, in turn, aid our understanding of the marsupial immune system and support the development of specific immunological reagents for research and wildlife conservation purposes.

Angioarchitecture and morphology of temporomandibular joint of Monodelphis domestica

The opossum Monodelphis domestica presents movement of the temporomandibular joint (TMJ) reflecting adaptation to eating habits similar to movement in humans, but the structure of the TMJ is not yet known. Thus, nine young M. domestica, of both sexes were weighed, anesthetized with xylazine (10 mg kg(-1) ), and ketamine (70 mg kg(-1) ) and processed for: 1. The analyses of the macroscopic angioarchitecture after latex injection, as well as the topography of the TMJ; 2. The analysis of microvascularization after injection of Mercox resin and corrosion of soft tissue with NaOH using scanning electron microscopy and; 3. The histological evaluation of the TMJ with an optical microscope. Macroscopic analysis of the latex injected vessels revealed the distribution of the arteries from the common carotid artery, receiving branches of the superficial temporal and maxillary arteries. The mandibular condyle has the long axis in the lateral-lateral direction, and is convex in the anterior-posterior direction. Its topography was determined in relation to the eye and external acoustic meatus. With scanning electron microscopy, microvascularization consists of arterioles of varying diameter (85-15 µm) of the meandering capillary network in the retrodiscal region, and a network of straight capillaries in the TMJ anterior region. Via light microscopy the TMJ has similar histological features to those of humans. These macroscopic, microscopic and ultrastructural data from TMJ of the M. domestica could be a suitable model for TMJ physiology and pathophysiology studies for then speculate on possible human studies. Microsc. Res. Tech. 79:806-813, 2016. © 2016 Wiley Periodicals, Inc.

Evolving strategies for cancer and autoimmunity: back to the future

Although current thinking has focused on genetic variation between individuals and environmental influences as underpinning susceptibility to both autoimmunity and cancer, an alternative view is that human susceptibility to these diseases is a consequence of the way the immune system evolved. It is important to remember that the immunological genes that we inherit and the systems that they control were shaped by the drive for reproductive success rather than for individual survival. It is our view that human susceptibility to autoimmunity and cancer is the evolutionarily acceptable side effect of the immune adaptations that evolved in early placental mammals to accommodate a fundamental change in reproductive strategy. Studies of immune function in mammals show that high affinity antibodies and CD4 memory, along with its regulation, co-evolved with placentation. By dissection of the immunologically active genes and proteins that evolved to regulate this step change in the mammalian immune system, clues have emerged that may reveal ways of de-tuning both effector and regulatory arms of the immune system to abrogate autoimmune responses whilst preserving protection against infection. Paradoxically, it appears that such a detuned and deregulated immune system is much better equipped to mount anti-tumor immune responses against cancers.

OX40 and CD30 signals in CD4(+) T-cell effector and memory function: a distinct role for lymphoid tissue inducer cells in maintaining CD4(+) T-cell memory but not effector function

CD4(+) effector and memory T cells play a pivotal role in the development of both normal and pathogenic immune responses. This review focuses on the molecular and cellular mechanisms that regulate their development, with particular focus on the tumor necrosis factor superfamily members OX40 (TNFRSF4) and CD30 (TNFRSF8). We discuss the evidence that in mice, these molecular signaling pathways act synergistically to regulate the development of both effector and memory CD4(+) T cells but that the cells that regulate memory versus effector function are distinct, effectively allowing the independent regulation of the memory and effector CD4(+) T-cell pools.

Lymphoid tissue inducer cells: innate cells critical for CD4+ T cell memory responses?

Lymphoid tissue inducer cells (LTi) are a relatively new arrival on the immunological cellular landscape, having first been characterized properly only 15 years ago. They are members of an emerging family of innate lymphoid cells (ILCs). Elucidation of their function reveals links not only with the ancient innate immune system, but also with adaptive immune responses, in particular the development of lymph nodes and CD4(+) T cell memory immune responses, which on one hand underpin the success of vaccination strategies, and on the other hand drive many human immunologically mediated diseases. This perspective article is not an exhaustive account of the role of LTi in the development of lymphoid tissues, as there have been many excellent reviews published already. Instead, we combine current knowledge of genetic phylogeny and comparative immunology, together with classical mouse genetics, to suggest how LTi might have evolved from a primitive lymphocytic innate cell in the ancestral 500-million-year-old vertebrate immune system into a cell critical for adaptive CD4(+) T cell immune responses in mammals.

Lymphoid tissue inducer cells and the evolution of CD4 dependent high-affinity antibody responses

Phylogeny indicates that in mammals memory CD4-dependent antibody responses evolved after monotremes split from the common ancestor of marsupial and eutherian mammals. This was strongly associated with the development of segregated B and T cell areas and the development of a linked lymph node network. The evolution of the lymphotoxin beta receptor in these higher mammals was key to the development of these new functions. Here, we argue that lymphoid tissue inducer cells played a pivotal role not only in the development of organized lymphoid structures but also in the subsequent genesis of the CD4-dependent class-switched memory antibody responses that depend on an organized infrastructure to work. In this review, we concentrate on the role of this cell type in the making of a tolerant CD4 T cell repertoire and in the sustenance of CD4 T cell responses for protective immunity.

Those other mammals: the immunoglobulins and T cell receptors of marsupials and monotremes

This review summarizes analyses of marsupial and monotreme immunoglobulin and T cell receptor genetics and expression published over the past decade. Analyses of recently completed whole genome sequences from the opossum and the platypus have yielded insight into the evolution of the common antigen receptor systems, as well as discovery of novel receptors that appear to have been lost in eutherian mammals. These species are also useful for investigation of the development of the immune system in organisms notable for giving birth to highly altricial young, as well as the evolution of maternal immunity through comparison of oviparous and viviparous mammals.

On the genomics of immunoglobulins in the gray, short-tailed opossum Monodelphis domestica

Annotated maps of the IGH, IGK, and IGL loci in the gray, short-tailed opossum Monodelphis domestica were generated from analyses of the available whole genome sequence for this species. Analyses of their content and organization confirmed a number of previous conclusions based on characterization of complementary DNAs encoding opossum immunoglobulin heavy and light chains and limited genomic analysis, including (a) the predominance of a single immunoglobulin heavy chain variable region (IGHV) subgroup and clan, (b) the presence of a single immunoglobulin (Ig)G subclass, (c) the apparent absence of an IgD, and (d) the general organization and V gene complexity of the IGK and IGL light chain loci. In addition, several unexpected discoveries were made including the presence of a partial V to D, germline-joined IGHV segment, the first germline-joined Ig V gene to be found in a mammal. In addition was the presence of a larger number of IGKV subgroups than had been previously identified. With this report, annotated maps of the major histocompatibility complex, T-cell receptor, and immunoglobulin loci have been completed for M. domestica, the only non-eutherian mammalian species for which this has been accomplished, strengthening the utility of this species as a model organism.

High levels of variability in immune response using antigens from two reproductive proteins in brushtail possums

Immune-based fertility control is being considered as an effective long-term approach for controlling the pest brushtail possum (Trichosurus vulpecula) population in New Zealand. This relies heavily on the immune response of each immunised possum. A strong and lasting immune response in the majority of individuals in a population is essential. In this study, possums and the model macropod species, the tammar wallaby (Macropus eugenii) were immunised with either a luteinising hormone or androgen receptor synthetic peptide coupled to the carrier molecule KLH (keyhole limpet haemocyanin). The antibody response of wallabies to the antigens was relatively uniform. In contrast, the possum immunoglobulin response to both synthetic peptides and KLH was variable. The apparent high level of variation in the immune response of possums raises questions about the feasibility of using these two antigens to control possum numbers in New Zealand.

Molecular cloning and characterization of the polymorphic MHC class II DBB from the tammar wallaby (Macropus eugenii)

Genes of the major histocompatibility complex (MHC) have been characterized in all extant lineages of mammals. The tammar wallaby (Macropus eugenii) is well established as a model marsupial species; however, no classical MHC sequences have been described from this species. We have isolated two MHC class II beta-chain sequences from a tammar wallaby spleen cDNA library using a tammar MHC class II beta probe. These sequences belong to the marsupial MHC class II DBB gene family. Two additional DBB sequences were amplified from tammar wallaby genomic DNA. All four sequences were obtained from the same individual, indicating that there are at least two DBB loci in the tammar wallaby.

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.

Immunoglobulin genetics of marsupials

Until recently, studies of marsupial immunoglobulins were limited to primarily protein analyses, such as Protein A binding and immunological cross-reactivity to eutherian immunoglobulins to draw conclusions about the isotypes present in metatherians. This left an interesting gap in our knowledge of the evolution of vertebrate, more specifically mammalian, antibodies and provided little insight into the diversity of marsupial antibodies. Recently, however, there has been a flurry of papers from multiple laboratories describing, at the molecular level, the heavy and light chain classes present in marsupials with some analysis of the expressed repertoires. These studies have provided the evidence to determine when some of the uniquely mammalian isotypes, e.g. IgG and IgE, appeared in evolution, and are a first look at the complexity of heavy and light chain variable regions in a metatherian. Here we review what was known prior to the cloning of marsupial Ig genes and what we have learned recently.

Development of the immune system and immunological protection in marsupial pouch young

At birth the tissues of marsupial immune system are underdeveloped. The young animal is not immunocompetent. Histological and immunohistochemical studies of pouch young epithelial tissues provide a clear picture of tissue development but the timing of onset of immunocompetence awaits definition. The survival of the neonatal marsupial in a microbially rich environment is dependent on maternal strategies, including immunoglobulin transfer via milk and, in some species, prenatally via the yolk sac placenta. It is also likely that pouch secretions play a role. This review summarizes our current knowledge of the pathway of immunological development in marsupials and the protection and threats afforded by the pouch environment.

Cloning of marsupial T cell receptor alpha and beta constant region cDNAs

Partial cDNAs encoding the tammar wallaby (Macropus eugenii) T cell receptor alpha constant region (TCRalphaC) and T cell receptor beta constant region (TCRbetaC) were obtained using reverse transcriptase-coupled polymerase chain reaction (RT-PCR). These PCR products were used to screen a brushtail possum (Trichosurus vulpecula) lymph node cDNA library, resulting in the isolation of clones containing the complete coding regions for TCRalphaC and TCRbetaC. These constitute the first marsupial T cell receptor sequences to have been elucidated. Sequence analysis of the T. vulpecula constant region revealed a considerable level of sequence identity with TCR of other species, particularly eutherian mammals, at both the nucleic acid and amino acid levels. At the nucleotide level, 65.8% sequence identity was calculated for the T. vulpecula and human TCRalphaC sequences, with 55.9% identity at the amino acid level. For TCRbetaC, the T. vulpecula and human beta1 sequence identity at the nucleotide level was 75.1% and at the amino acid level, 67.0%. Phylogenetic analyses based on the T. vulpecula sequences indicated that these sequences are basal to, but also most closely related with, TCRalphaC and TCRbetaC homologues from eutherian mammals, consistent with the current views of both mammalian and TCR evolution.

Isolation and comparison of the IgM heavy chain constant regions from Australian (Trichosurus vulpecula) and American (Monodelphis domestica) marsupials

cDNAs encoding IgM heavy chain constant region (Cmu) were isolated from two metatherians (marsupials)--the Australian common brushtail possum (Trichosurus vulpecula) and the South American grey short-tailed opossum (Monodelphis domestica). Analysis of the sequences suggested that they correspond to the secreted form of Cmu in both species. The domain size and structure of the marsupial Cmu sequences were compared with other Cmu sequences and a high degree of conservation throughout vertebrate evolution was observed. Amino acid sequence comparisons revealed a marked level of sequence similarity between the two marsupial sequences (79%), relatively high similarity between the marsupials and eutherians (63%), and lower similarities between marsupials and birds (45%), marsupials and amphibians (47%), marsupials and reptiles (45%) and marsupials and fish (37%). These data allow the incorporation of metatherians into the study of mammalian IgM evolution.

The complement system of the marsupial Monodelphis domestica

The activation requirements and pathways of the serum C' system of the marsupial Monodelphis domestica were characterized using standard hemolytic procedures. The existence of distinct classical and alternative activation pathways was established on the basis of their ionic requirements, hemolytic capacity at different temperatures, kinetics of hemolysis, and differential susceptibility to the classical pathway inhibitor carrageenan. For the most part, the activities of these pathways were influenced by factors and conditions in a manner similar to the way they affect the activity of eutherian complement. These observations provide further support for the idea that Monodelphis domestica would serve as a useful model for comparative immunological studies in mammals.