Anti-CD8 alpha Antibody [OX-8] (A86620)

Consistent with their role in host defense, mature dendritic cells (DCs) from central lymphoid organs preferentially prime for T helper cell type 1 (Th1)-polarized immunity. However, the "default" T helper response at mucosal surfaces demonstrates Th2 polarity, which is reflected in the cytokine profiles of activated T cells from mucosal lymph nodes. This study on rat respiratory tract DCs (RTDCs) provides an explanation for this paradox. We demonstrate that freshly isolated RTDCs are functionally immature as defined in vitro, being surface major histocompatibility complex (MHC) II lo, endocytosishi, and mixed lymphocyte reactionlo, and these cells produce mRNA encoding interleukin (IL)-10. After ovalbumin (OVA)-pulsing and adoptive transfer, freshly isolated RTDCs preferentially stimulated Th2-dependent OVA-specific immunoglobulin (Ig)G1 responses, and antigen-stimulated splenocytes from recipient animals produced IL-4 in vitro. However, preculture with granulocyte/macrophage colony stimulating factor increased their in vivo IgG priming capacity by 2-3 logs, inducing production of both Th1- and Th2-dependent IgG subclasses and high levels of IFN-gamma by antigen-stimulated splenocytes. Associated phenotypic changes included upregulation of surface MHC II and B7 expression and IL-12 p35 mRNA, and downregulation of endocytosis, MHC II processing- associated genes, and IL-10 mRNA expression. Full expression of IL-12 p40 required additional signals, such as tumor necrosis factor alpha or CD40 ligand. These results suggest that the observed Th2 polarity of the resting mucosal immune system may be an inherent property of the resident DC population, and furthermore that mobilization of Th1 immunity relies absolutely on the provision of appropriate microenvironmental costimuli.

BACKGROUND:

This study examined the ability of lipopolysaccharide (LPS) to affect glioma and glioma stem-like cells (GSCs) in vitro and to induce antitumor immunity in vivo and the role of TLR4 in these processes.

METHODS:

Using RT-PCR and immunohistochemistry, we examined the expression of TLR4 in 34 glioblastoma clinical samples. Using real time-PCR, western blot and ELISA analyses, the effect of LPS stimulation on the expression of immune related molecules was evaluated in RG2 and U87 GSCs. Control or LPS-pretreated RG2 GSCs were intracranially or subcutaneously implanted into wild-type or nude Fisher 344 rats. Histopathological examinations were used to assess tumor progression and immune infiltration and Kaplan-Meier analyses to compare survival times of the animal models.

RESULTS:

TLR4 was highly expressed in glioblastoma clinical samples. In vitro LPS stimulation for 6 h significantly altered expression of immune related molecules in RG2 and U87 GSCs. However, prolonged LPS stimulation diminished this effect. Rats inoculated intracranially with LPS-pretreated RG2 GSCs survived significantly longer than rats inoculated with control RG2 GSCs. In vivo, LPS-pretreated RG2 GSCs expressed higher levels of MHC molecules, CXCL10 and TNF-α and recruited more CD8⁺ lymphocytes. However, intratumoral LPS treatment was not equally beneficial. Furthermore, the in vitro and in vivo effects of LPS stimulation appeared to be largely TLR4-dependent.

CONCLUSION:

LPS pretreatment promotes the recognition and eradication of tumor GSCs in vivo when the immune function of the tumor-bearing host is intact. In addition, our data indicate a complex relationship between bacterial infection and glioma prognosis.

Extracellular matrices isolated from several mammalian organs/tissues have found several clinical uses as xenografts or implants. However, they may cause complications because of adverse immunologic reactions. Scaffolds that promote favorable graft-acceptance reaction are preferred for fabricating xenografts. The objective of this study was to evaluate the immunogenic potential of a porcine cholecyst-derived scaffold (CDS), prepared by a non-detergent/enzymatic method, in comparison with jejunum and urinary bladder-derived scaffolds in a rat subcutaneous model. Key graft-rejection/acceptance reaction was evaluated at the site of implantation by studying the occurrence and/or function of immunocompetent cells in the tissue reaction. There was differential occurrence of M1-macrophage, M2-macrophage, T-helper cells, T-cytotoxic cells, B-cells, and mast cells in the tissue reaction and the CDS attracted few cells compared with other scaffolds. Real-time polymerase chain reaction for evaluating mRNA of functional markers like inducible nitric oxide synthase (M1 macrophage), arginase 1 (M2 macrophage), interferon gamma (TH1 lymphocytes), and interlukin-4 (TH2 lymphocytes) suggested that the CDS, compared with the scaffolds prepared from small intestine and urinary bladder, elicited M2 macrophage and TH2 lymphocyte polarization that are congenial graft-acceptance reactions. The results indicated that CDS has less immunogenic potential compared with the scaffolds prepared from jejunum and urinary bladder when used as subcutaneous graft in rats. It was concluded that CDS is a promising animal-derived xenograft for biomedical application.

Expression of CD44 is involved in the maturation as well as the homing of haemopoietic progenitor cells. Whether these processes are mediated by CD44 standard (CD44s) or variant (CD44v) isoforms is unknown. To assign functional activities of CD44 in haemopoiesis of the rat to distinct isoforms, ligand binding of haemopoietic progenitor cells was inhibited by monoclonal antibodies recognizing an epitope on CD44s (Ox50) or CD44 exon v6, (1.1ASML). The vast majority of rat bone marrow cells (BMC) as well as stromal cells and non-adherent cells in long-term bone marrown culture (LTBMC) expressed CD44s. Bone marrow cells and non-adherent cells in LTBMC, but not the stromal cells, also contained a population of large and granulated cells, which stained with anti-CD44v6. In vivo and in vitro reconstitution experiments revealed that homing of BMC as well as settlement on stromal elements was influenced exclusively by anti-CD44s, which also inhibited proliferation of progenitor cells. Anti-CD44v6 had no influence on homing and seeding, but interfered with stroma formation and progenitor maturation. Finally, restoration of functional activity of T-lineage cells was impaired in the presence of anti-CD44v6. The data indicate that CD44s and CD44v6 fulfilled distinct functions in haemopoiesis of the rat. Although CD44s facilitated homing and expansion of stem cells, progenitor cells, CD44v6 was involved in differentiation processes, particularly of lymphoid progenitor cells.

We describe a method for immunohistochemical localization of T-cells, CD4+ T-cells, CD8+ T-cells, B-cells, activated lymphocytes, major histocompatibility complex (MHC) class II antigens, macrophages, dendritic cells, and granulocytes in rat and mouse tissue fixed in periodate-lysine-paraformaldehyde (PLP) and embedded in paraffin. Rat and mouse spleen and eyes were fixed in PLP for 18-24 hr, rapidly dehydrated, infiltrated under vacuum with paraffin at 54 degrees C, sectioned, and stained with appropriate monoclonal antibodies (MAbs). Sections of PLP-fixed, paraffin-embedded spleen were compared with acetone-fixed frozen spleen sections with respect to morphology and staining quality. Nine of 10 MAbs to rat antigens and eight of nine MAbs to mouse antigens stained paraffin sections equally or more intensely than frozen sections. The two MAbs that showed weaker staining still gave good staining on paraffin sections. Paraffin-embedded rat and mouse eyes were easier to section serially than frozen eyes, showed superior morphology, and individually stained cells were readily identified. Therefore, a combination of PLP fixation and low-temperature paraffin embedding permits detection of the major types of immune cell in rat and mouse tissues while maintaining good morphology, particularly in diseased, damaged, or delicate tissues.

A new method of thymus transplantation is introduced, in which the graft is directly connected with the recipient's vascular system. This procedure was used both in euthymic rats and congenitally athymic nude rats. At all tested intervals after transplantation thymus grafts hardly differed from the recipient's own thymus in immunohistology and lymphocyte yield. In athymic nude rats, T cell-dependent immunity, tested by mitogen- and alloantigen-induced T cell responses, as well as by antibody production and delayed-type hypersensitivity after ovalbumin administration, showed that vascular thymus grafts could generate T cell functions to euthymic control levels. We conclude that the technique of vascular thymus transplantation represents a valuable tool, either in fundamental research on thymus function, or for the purpose of immune (re)constitution.

The phenotype of 27 Moloney murine leukemia virus-induced rat thymic lymphomas and 36 cell lines derived from these tumors was determined by using 18 monoclonal antibodies directed against hematopoietic cell surface determinants. The cell lines and the primary tumors from which they were derived were clonally related as determined by the pattern of provirus integration and the pattern of rearrangement of the T-cell receptor beta and delta and Igh loci. The differentiation phenotype of the primary tumors and the cell lines derived from them were related. The differences observed between the primary tumors and the cell lines could be explained either by the selection of subpopulations of tumor cells during establishment in culture or by the phenotypic instability of the tumor cells. One cell line (LE3Sp) underwent the transition from a CD4+ CD8+ to a CD4+ CD8- phenotype following exposure to interleukin-2 in culture. Both the primary tumors and the cell lines derived from them express a wide range of phenotypes which correspond to multiple stages in T-cell development. This observation suggests that the pleiomorphism of retrovirus-induced lymphomas, which had been suggested previously from the analysis of mouse tumors, is an intrinsic property of the process of oncogenesis and is not due to the transformation of different types of cells by spontaneously arising leukemogenic variants of the inoculated virus. The wide spectrum of phenotypes expressed by these tumors suggests that Moloney murine leukemia virus may infect and transform T cells at various stages of development. Alternatively, the target cells may be immature T-cell precursors which, following transformation, continue to differentiate. A host of early findings, suggesting that the repertoire of target cells is restricted to poorly differentiated hematopoietic progenitors, and the ability of the LE3Sp cell line to differentiate in culture indicate that the latter possibility may be more likely. The data in this report address the extent and mechanism of the phenotypic variability of retrovirus-induced rodent T-cell lymphomas. In addition, they demonstrate the potential usefulness of the T-cell lymphoma lines we have established in studies of oncogenesis and T-cell differentiation.

The T-cell antigen receptor (TCR) complex is the key structure involved in signal transduction in T cells. To analyze associations between the TCR complex and other molecules, immunoprecipitations were carried out, followed by phosphorylation of molecules in vitro by tyrosine kinases associated with the precipitated molecules. This provided a sensitive assay for molecular complexes, and associations were demonstrated between the TCR complex and the surface antigens CD2, CD4, or CD8 and CD5 in normal rat T cells. The complexes were readily seen in immunoprecipitates from Brij 96 but not Nonidet P-40 detergent extracts. The multimolecular complexes are associated with the internal tyrosine kinases p56lck and p59fyn. The presence of p56lck associated with CD4 or CD8 was also examined in early thymocytes, natural killer cells, and macrophages. The kinase was present in all cases except that of normal macrophages.