Clustering of antigenic determinants on H-2 molecules

The spatial relationship of individual antigenic determinants on H-2Kk and H-2Db molecules was investigated with seven different monoclonal anti-H-2Kk and seven anti-H-2Db antibodies. In these studies the binding of radiolabeled monoclonal anti-H-2 to target cells was competed by addition of various cold anti-H-2 antibodies. The results indicate that on both H-2Kk and H-2Db molecules the antigenic determinants are arranged in two spatially separated clusters. Thus, antibodies to determinants within a cluster show mutual inhibition of binding but do not block the binding of antibodies to the other cluster, and vice versa. Furthermore, in the case of H-2Db antigens it was observed that binding of antibodies to one cluster would considerably enhance the binding of antibodies to the other cluster. A preliminary Scatchard analysis indicated that the enhancing antibody did not alter the affinity of the radiolabeled antibody, but led to an increase of available binding sites on the cell membrane. In addition, binding inhibition studies revealed that the conventional private specificity H-2.2 of H-2Db consists of at least two independent sites on the molecule.     

Changes in the accessibility of chromatin antigenic determinants induced by different influences

The accessibility of protein antigenic determinants of rat thymocyte chromatin was studied in a reaction of complement fixation, using antisera from animals immunized with chromatin or non-histone proteins and control sera containing natural antichromatin IgG. It was shown that the bulk of the antigenic determinants of intact chromatin are inaccessible for antibodies. The reactivity of chromatin in the complement fixation assay increases after ultrasonication or irradiation in vitro as well as the enzymatic cleavage of chromatin down to nucleosomes and their oligomers in dying thymocytes in vivo. This effect can mainly be due to changes of chromatin compactization.     

A 64 kDa protein from Mycobacterium bovis BCG shares the same antigenic determinants with line 10 hepatoma cells and has anti-line 10 tumor activity.

A 64 kilodalton (kDa) surface protein was isolated from the water-extracted materials from Mycobacterium bovis strain BCG, the determinants of which are antigenically shared by a 64 kDa major surface antigenic component of line 10 hepatoma cells. The 64 kDa protein showed anti-line 10 tumor activity in pre-immunized guinea pigs, and this suggest that the BCG 64 kDa protein is probably identical with the tumor specific antigen.     

Gap junctions in several tissues share antigenic determinants with liver gap junctions.

Using affinity-purified antibodies against mouse liver gap junction protein (26 K), discrete fluorescent spots were seen by indirect immunofluorescence labelling on apposed membranes of contiguous cells in several mouse and rat tissues: pancreas (exocrine part), kidney, small intestine (epithelium and circular smooth muscle), Fallopian tube, endometrium, and myometrium of delivering rats. No reaction was seen on sections of myocardium, ovaries and lens. Specific labelling of gap junction plaques was demonstrated by immunoelectron microscopy on ultrathin frozen sections through liver and the exocrine part of pancreas after treatment with gold protein A. Weak immunoreactivity was found on the endocrine part of the pancreas (i.e., Langerhans islets) after glibenclamide treatment of mice and rats, which causes an increase of insulin secretion and of the size as well as the number of gap junction plaques in cells of Langerhans islets. Furthermore, the affinity purified anti-liver 26 K antibodies were shown by immunoblot to react with proteins of similar mol. wt. in pancreas and kidney membranes. Taken together these results suggest that gap junctions from several, morphogenetically different tissues have specific antigenic sites in common. The different extent of specific immunoreactivity of anti-liver 26 K antibodies with different tissues is likely due to differences in size and number of gap junctions although structural differences cannot be excluded.     

Distinct phenotypic expression of immunogenicity and immunosensitivity in sublines of a tumor

Continuous in vitro or in vivo passage of a BALB/c leukemia has resulted in generation of 2 immunologically distinct sublines. The subline maintained by in vitro passage failed to stimulate an allogeneic response but was susceptible to lysis by alloreactive cytotoxic cells. Conversely, the subline maintained by in vivo passage induced an allogeneic response but was resistant to lysis by cytotoxic T lymphocytes (CTL) reactive to H-2d antigens. Resistance to lysis occurred despite expression of H-2d antigens in a form recognizable by differentiated alloreactive CTL, as determined by cold-target inhibition experiments. Moreover, resistance was immunologically specific, in that the subline was susceptible to immune lysis mediated through recognition of other determinants. The results imply that the display and/or orientation of antigen in the cell membrane of these sublines that is required for a lytic event is distinct from the antigen expression necessary for immunologic recognition.     

Novel antigenic determinants from peptidorhamnomannans of Sporothrix schenckii

Antisera were raised in rabbits against acetone-dried yeast-likeand mycelium forms of Sporothrix schenckii. These antisera weretested for immunoprecipitation of peptidorhamnomannans isolatedfrom both cell types. Both antisera reacted strongly with S.schenckiipeptidorhamnomannans, but the reactions were weak with ß-eliminatedpeptidopolysaccharides. These antisera did not recognize theSaccharomyces cerevisiae mannoprotein, and reacted poorly withCeratocystis (Ophiostoma) stenoceras cell wall glycopeptides.Since ß-eliminated glycopeptides were poorly reactive,we investigated the activity of O-glycosidically linked oligosaccharideswhich were liberated from the peptidorhamnomannans by mild alkalinehydrolysis, using a hapten inhibition test. The rates of inhibitionshowed that the immunodominant epitopes in O-linked tetra- andpentasaccharides had the following novel structures:     

Antigen-specific helper T cells recognize determinants encoded in the H-2D region of the H-2 gene complex

Observations have frequently been interpreted as showing that the helper T cells which collaborate with alloantigen-specific cytotoxic T-cell precursors can only recognize antigens encoded in the I region of the H-2 gene complex. An experimental system is described here that allows analysis of the recognition repertoire of these helper cells. CBA helper T-cell precursors can be primed in vitro to antigens encoded in the H-2 ^b gene complex. These helpers can then be tested for the existence of a subset of helper cells which recognize antigens encoded in the D region of H-2 ^b haplotype. CBA thymocytes were used as a source of cytotoxic T-cell precursors that respond poorly in the absence of exogeneous helper activity. The source of alloantigen was varied by using irradiated spleen cells from various (BALB/c × recombinant)F₁ hybrid mice as stimulator cells. When the stimulator cell bears BALB/c determinants recognized by the cytotoxic T-cell precursor and also bears only the D region antigens of the H-2 ^b haplotype, an anti-BALB/c cytotoxic response is generated only if the anti-H-2^b helper population contains cells able to recognize H-2D^b. A positive cytotoxic response was obtained, indicating that helper cells are not limited to recognition of I region antigens and can efficiently recognize antigens encoded in the D region of the H-2 gene complex. This was confirmed by the demonstration of helpers specific for H-2D^d. We were unable to detect any evidence for Ia-restricted recognition of the H-2D alloantigens, suggesting that, as for cytotoxic T lymphocytes (CTL), helper cell recognition of class I alloantigens is an unrestricted event.     

Hedgehog信号通路在肿瘤中作用的研究进展

癌的发生是一个多因素多步骤的过程,同时伴随着一系列致癌因素所导致的基因突变,以及某些信号通路的异常激活。hedgehog（HH）信号通路参与了正常的胚胎发育过程以及组织的创伤与修复,特别是干细胞的自我更新,但它的异常激活却在多种人类恶性肿瘤中有发生。本文集中介绍HH在癌的发生、增殖、浸润及转移中所起的重要作用,通过对其致癌机制的综述,阐明它将可能成为一个有效治疗靶点,从而为肿瘤的防治提供了更多机遇。     

Isolation and antigenic characterization of the product of a third polymorphic H-2 locus, H-2L.

The serology, immunochemistry, and genetics of the product(s) of a third H-2 locus, H-2L (previously designated D') have been studied by using an antiserum raised in BALB/c H-2db mutant mice against tissues from the wild type strain, BALB/c. Genetic mapping studies and sequential immunoprecipitation experiments both indicate that this antiserum reacts specifically with L molecules. These results imply that an H-2L product is antigenically undetectable in BALB/c-H-2db mice and that the lesion in this mutant is confined to the H-2L and not the H-2D locus. Two new specificities, H-2.64 and H-2.65, are defined by the reactivity of anti-L serum on allogeneic cells, and the strain distribution of these specificities suggests the existence of at least three H-2L alleles. This third H-2 locls is therefore polymorphic and in view of this and other similarities to the H-2K and H-2D loci, it must be considered in any evolutionary models dealing with the origin of multiple subloci of the major histocompatibility complex.     

Allo-I-J determinants participate in maintenance of neonatal H-2 tolerance

To evaluate the role of IJ antigens in maintenance of the tolerant state in adult H-2 tolerant mice, we have attempted to abolish tolerance by injecting monoclonal antibodies (mab) specific for host, donor, or third party IJ antigens into adult H-2 tolerant mice. Abolition of tolerance was evidenced by the rejection of fresh test skin grafts bearing the tolerated antigens. Whole H-2 tolerant mice treated with anti-IJ mab specific for donor (allo) IJ antigens rejected their test skin grafts, indicating that tolerance had been abolished. When two other types of tolerant mice were tested, we found that mice tolerant of class II antigens alone, but not mice tolerant of an IJ thru D disparity, were susceptible to the anti-donor IJ mab treatment. In addition, adult tolerant mice were unaffected by treatment with either anti-host or anti-third party IJ mab. When tested in vitro, lymphoid cells from tolerant mice, the tolerance of which was abolished by anti-IJ mab, remained unresponsive to the tolerogen, just as untreated (control) tolerant mice, in several in vitro assays (e.g., mixed lymphocyte reaction, cytotoxic T cell precursor frequency and bulk cell-mediated lysis without growth factor). Mice treated with antidonor IJ mab, however, unlike mice treated with anti-host or third party IJ mab, were capable of generating tolerogen-specific T cells in the absence of exogenous growth factor. Thus in the strain combinations we used, adult mice tolerant of either the entire H-2 region or of the class II major histocompatibility complex region alone are susceptible to abolition of the tolerant state by treatment with anti-donor IJ mab. Coincidentally, lymphoid cells from these mice generate sufficient endogenous T helper activity to activate the tolerogen-specific cytotoxic T cells. We suspect that these latter cells may be responsible for rejection of grafts bearing the tolerated antigens.     

Analysis of the copy number profiles of several tumor samples from the same patient reveals the successive steps in tumorigenesis

We present a computational method, TuMult, for reconstructing the sequence of copy number changes driving carcinogenesis, based on the analysis of several tumor samples from the same patient. We demonstrate the reliability of the method with simulated data, and describe applications to three different cancers, showing that TuMult is a valuable tool for the establishment of clonal relationships between tumor samples and the identification of chromosome aberrations occurring at crucial steps in cancer progression.     

Differential lack of class I H-2d antigen expression by sublines of the BALB/c S49 T cell lymphoma

Five different sublines of the BALB/c murine S49.1 T cell lymphoma were found to exhibit distinct patterns of absence of detectable H-2d class I major histocompatibility antigen expression. The results were demonstrated and verified by a) the generation of H-2Kd-, H-2Dd,Ld-, and H-2Ld-specific cytotoxic T lymphocytes that were assayed on S49.1 target cell lines, b) antibody-mediated cytotoxicity with the use of anti-H-2d monoclonal reagents, and c) flow microfluorometry. The five lines investigated were S49.1, T-25, T-25ADH, Thy-1-, and 100/0. None of these lines expressed detectable levels of Ld. S49.1 expressed both Kd and Dd, T-25 and T-25ADH expressed Dd but not Kd or Ld, Thy-1- expressed Kd but not Dd or Ld, and 100.0 did not express any detectable amounts of Kd, Dd, or Ld. These results indicate that K and D (and L) antigens can be expressed independently of each other and suggest that expression of class I antigens is controlled in a locus-specific manner.