Characterization of new monoclonal antibodies against porcine lymphocytes: molecular characterization of clone 7G3, an antibody reactive with the constant region of the T-cell receptor δ-chains

Porcine T lymphocytes and NK cells--an update

Natural killer (NK) cells represent an important cell population of the innate immune system with the ability to attack spontaneously pathogen-infected and malignant body cells as well as to produce immune-regulatory cytokines. T lymphocytes belong to the adaptive immune system and perform a wide array of functions in immune regulation, inflammation and protective immune responses. In this review we summarize the current knowledge about the phenotype and functional characteristics of these two cell populations in swine. Porcine NK cells can be distinguished from T cells by the complex phenotype perforin+ CD3(-)CD4(-)CD5(-)CD6(-)CD8alpha+CD8beta(-)CD11b+CD16+. Investigations so far show that these cells have the capacity to lyse virus-infected target cells and respond to various regulatory cytokines. Such cytokines can induce interferon-gamma (IFN-gamma) production in porcine NK cells, as well as the up-regulation of effector/activation molecules like perforin and CD25. Porcine T cells can be divided into a number of subpopulations, including a prominent fraction of T cells expressing T-cell receptors (TCR) with gammadelta-chains. Like TCR-alphabeta T cells, these TCR-gammadelta T cells can express CD8alpha and MHC class II, two molecules which in swine seem to be correlated with an activation status of T cells. Functional properties of these cells seem to include cytolytic activity as well as antigen presentation; however, both aspects require further investigation. Like in other species, TCR-alphabeta T cells in swine comprise MHC class-I restricted cytolytic T cells, T-helper cells and recently identified regulatory T cells. We summarize data on the phenotype and function of these cells including memory cell formation. Current knowledge suggests that MHC class-I restricted cytolytic T cells can be identified by the expression of CD8alphabeta heterodimers. T-helper cells express CD4 as well as other activation-related markers, including CD8alpha, MHC class II and CD45RC. Porcine regulatory T cells have a phenotype similar to that of mouse and humans: CD4+CD25+Foxp3+. First results indicate that these cells can suppress proliferation of other T cells and produce IL-10. Finally, the abundant expression of swine-specific activation markers CD8alpha and MHC class II on T cells and NK cells is discussed in more detail.

Membrane markers of the immune cells in swine: an update

Besides their breeding value, swine are increasingly used as biomedical models. As reported in three international swine clusters of differentiation (CD) workshops and in the animal homologue section of the last workshop for the determination of human leukocyte differentiation antigens (HLDA 8), characterisation of leukocyte surface antigens by monoclonal antibodies and other molecular studies have determined the cell lineages and blood leukocyte subsets implicated in the immune response, including cell adhesion molecules involved in cell trafficking. This review focusses on the current state of knowledge of porcine leukocyte differentiation and major histocompatibility complex (SLA) molecules. Examples of porcine particularities such as the double-positive T lymphocytes with the phenotype CD(4+)CD8(low) and CD(4-)CD8(low) alphabeta T cell subsets and the persistence of SLA class II after T-lymphocyte activation are illustrated, as well as the shared characteristics of the Artiodactyla group, such as the high proportion of gammadelta TcR (T cell receptor) T cells in blood and other lymphoid tissues. Furthermore, discrepancies between swine and humans, such as CD16 expression on dendritic cells and CD11b (wCD11R1) tissue distribution are outlined. The rapidly growing information should facilitate manipulation of the swine immune system towards improving disease control, and open new avenues for biomedical research using the pig as a model.

TCR and CD3 antibody cross-reactivity in 44 species

The production of monoclonal antibodies is very costly, and antibodies are only available for a limited number of species. Until a more cost effective method of antibody production is found, identification of cross-reactive antibodies is an alternative approach that can provide investigators studying immunity in minor species with valuable antibody reagents. Flow cytometry was used to test 21 monoclonal antibodies (mAb), raised against alphabeta and gammadelta T cell receptors and CD3 from human and five animal species, for cross-reactivity in 44 different species including 16 species of nonhuman primates, marsupials, carnivores, lagomorphs, rodents, ruminants, swine, cetacean, horse, birds, a reptile, and fish. Fifteen of the mAbs cross-reacted with orthologous molecules in one or more species. Two antibodies, anti-human TCR gammadelta (B1.1), and anti-human CD3 (SP34) were found to costain in 13 species of nonhuman primates. This study has identified valuable new reagents for studying T cell populations in different animal species and for the first time characterized antibodies useful for studying gammadelta T cell populations in many species of primates. These antibodies may be used for further immunity research in species with less well-characterized immune systems.

Porcine γδ T cells: Possible roles on the innate and adaptive immune responses following virus infection

gammadelta T cells recognise different types of antigen in alternative ways to alphabeta T cells, and thus appear to play a complementary role in the immune response. However, unlike alphabeta T cells, the role or function of gammadelta T cells is still unclear. As pigs possess a high proportion of circulating gammadelta T cells, they are suitable large animal model to study gammadelta T cell functions. This as yet has not been fully exploited, leaving porcine gammadelta T cell biology and its role in immunity in its infancy. Foot-and-mouth disease (FMD) high potency "emergency" vaccines are able to induce early protection from challenge and it has been suggested that, in part, there is some involvement of innate immune responses. The antigen component of the vaccine is able to stimulate purified naive pig gammadelta T cells and induce the mRNA of various cytokines and chemokines. This observation suggests that gammadelta T cells probably contribute to the early phase of the immune responses to FMD vaccination, and perhaps infection. A subset of these circulating gammadelta T cells display a phenotype similar to professional antigen presenting cells and are able to take up and present soluble antigen to CD4(+) T cells in a direct cell-cell interaction via MHC class II. This direct interaction between gammadelta T cells and CD4(+) T cells is likely to have a significant influence on the out come of the adaptive immune response.