Distribución de las células presentadoras de antígenos en las glándulas salivales

Las células presentadoras de antígenos profesionales como las células de Langerhans o las células dendríticas intersticiales del tejido conectivo, son las células capturadoras de antígenos más importantes del sistema inmune. En trabajos previos describimos variaciones numéricas y estructurales de las células dendríticas; con especial referencia a las células de Langerhans, en diversos epitelios del tracto digestivo. El propósito de este trabajo fue estudiar la distribución, en forma comparativa, de las células dendríticas en glándulas salivales mayores y menores de la mucosa oral. Material y métodos: para esta investigación se utilizaron muestras de glándulas salivales mayores y menores tomadas de ratas Wistar. Las muestras fueron procesadas utilizando técnicas de microscopía óptica convencional, electrónica e inmunohistoquímica. Los resultados muestran numerosas células dendríticas en los conductos salivares excretores (con epitelio estratificado) así como en el parénquima glandular. Aunque no detectamos diferencias estadísticas significativas entre los dos componentes glandulares analizados, nuestros hallazgos sugieren que, debido a su localización, estas células cumplen un rol fundamental en las defensas inmunes de la mucosa oral.

Immunostimulatory oligodeoxynucleotides containing the CpG motif are effective as immune adjuvants in tumor antigen immunization

Recent advances in our understanding of the immune response are allowing for the logical design of new approaches to cancer immunization. One area of interest is the development of new immune adjuvants. Immunostimulatory oligodeoxynucleotides containing the CpG motif (CpG ODN) can induce production of a wide variety of cytokines and activate B cells, monocytes, dendritic cells, and NK cells. Using the 38C13 B cell lymphoma model, we assessed whether CpG ODN can function as immune adjuvants in tumor antigen immunization. The idiotype served as the tumor antigen. Select CpG ODN were as effective as complete Freund’s adjuvant at inducing an antigen-specific antibody response but were associated with less toxicity. These CpG ODN induced a higher titer of antigen-specific IgG2a than did complete Freund’s adjuvant, suggesting an enhanced TH1 response. Mice immunized with CpG ODN as an adjuvant were protected from tumor challenge to a degree similar to that seen in mice immunized with complete Freund’s adjuvant. We conclude that CpG ODN are effective as immune adjuvants and are attractive as part of a tumor immunization strategy.

Peptide-specific cytotoxic T lymphocytes restricted by nonself major histocompatibility complex class I molecules: Reagents for tumor immunotherapy

Studies in melanoma patients have revealed that self proteins can function as targets for tumor-reactive cytotoxic T lymphocytes (CTL). One group of self proteins MAGE, BAGE, and GAGE are normally only expressed in testis and placenta, whilst another group of CTL recognized proteins are melanocyte-specific differentiation antigens. In this study we have investigated whether CTL can be raised against a ubiquitously expressed self protein, mdm-2, which is frequently overexpressed in tumors. The observation that T-cell tolerance is self major histocompatibility complex-restricted was exploited to generate CTL specific for an mdm-2 derived peptide presented by nonself major histocompatibility complex class I molecules. Thus, the allo-restricted T-cell repertoire of H-2d mice was used to isolate CTL specific for the mdm100 peptide presented by allogeneic H-2Kb class I molecules. In vitro, these CTL discriminated between transformed and normal cells, killing specifically Kb-positive melanoma and lymphoma tumors but not Kb-expressing dendritic cells. In vivo, the CTL showed antitumor activity and delayed the growth of melanoma as well as lymphoma tumors in H-2b recipient mice. These experiments show that it is possible to circumvent T-cell tolerance to ubiquitously expressed self antigens, and to target CTL responses against tumors expressing elevated levels of structurally unaltered proteins.

Constitutive tyrosine phosphorylation of the inhibitory paired Ig-like receptor PIR-B

PIR-A and PIR-B are activating and inhibitory Ig-like receptors on murine B lymphocytes, dendritic cells, and myeloid-lineage cells. The inhibitory function of PIR-B is mediated via its cytoplasmic immunoreceptor tyrosine-based inhibitory motifs, whereas PIR-A pairs with the Fc receptor common γ chain to form an activating receptor complex. In these studies, we observed constitutive tyrosine phosphorylation of PIR-B molecules on macrophages and B lymphocytes, irrespective of the cell activation status. Splenocyte PIR-B molecules were constitutively associated with the SHP-1 protein tyrosine phosphatase and Lyn protein tyrosine kinase. In Lyn-deficient mice, PIR-B tyrosine phosphorylation was greatly reduced. Unexpectedly, tyrosine phosphorylation of PIR-B was not observed in most myeloid and B cell lines but could be induced by ligation of the PIR molecules. Finally, the phosphorylation status of PIR-B was significantly reduced in MHC class I-deficient mice, although not in mice deficient in TAP1 or MHC class II expression. These findings suggest a physiological inhibitory role for PIR-B that is regulated by endogenous MHC class I-like ligands.

T cell functions in granulocyte/macrophage colony-stimulating factor deficient mice

Immunological functions were analyzed in mice lacking granulocyte/macrophage colony-stimulating factor (GM-CSF). The response of splenic T cells to allo-antigens, anti-mouse CD3 mAb, interleukin 2 (IL-2), or concanavalin A was comparable in GM-CSF +/+ and GM-CSF −/− mice. To investigate the responses of CD8+ and CD4+ T cells against exogenous antigens, mice were immunized with ovalbumin peptide or with keyhole limpet hemocyanin (KLH). Cytotoxic CD8+ T cells with specificity for ovalbumin peptide could not be induced in GM-CSF −/− mice. After immunization with KLH, there was a delay in IgG generation, particularly IgG2a, in GM-CSF −/− mice. Purified CD4+ T cells from GM-CSF −/− mice immunized with KLH showed impaired proliferative responses and produced low amounts of interferon-γ (IFN-γ) and IL-4 when KLH-pulsed B cells or spleen cells were used as antigen presenting cells (APC). When enriched dendritic cells (DC) were used as APC, CD4+ T cells from GM-CSF −/− mice proliferated as well as those from GM-CSF +/+ mice and produced high amounts of IFN-γ and IL-4. To analyze the rescue effect of DC on CD4+ T cells, supernatants from (i) CD4+ T cells cultured with KLH-pulsed DC or (ii) DC cultured with recombinant GM-CSF were transferred to cultures of CD4+ T cells and KLH-pulsed spleen cells from GM-CSF −/− mice. Supernatants from both DC sources contained a factor or factors that restored proliferative responses and IFN-γ production of CD4+ T cells from GM-CSF −/− mice.