H-2 mutation affecting immune response to Thy-1.1 antigen

Mouse thymus, thymus-derived lymphocytes, and brain share an antigen determined by gene at the Thy-1 locus in chromosome 9 (1). Two alleles have been identified at this locus: Thy-1(a), coding for antigen Thy-1.1 (or θ-AKR) present in AKR and seven other strains; and Thy-1(b), coding for antigen Thy-1.2 (or{teta}-C3H) and present in C3H and all the remaining inbred strains. Injection of AKR thymocytes into inbred mice carrying the Thy-1(b) allele results in an immune response that can be measured either serologically by determining the level of antibodies in the recipients’ serum (1) or by counting plaque- forming cells (PFC) detectable in spleens of the recipients by means of an assay, with AKR thymocytes as target cells(2). The magnitude of PFC and serum antibody responses after a single thymocyte injection depends on the genetic make-up of the recipient. Three genes controlling the PFC response to the Thy- 1.1 antigen have been identified: Ir-Thy-1A and Ir-Thy-1B, which are closely linked to the major histocompatibility complex (H-2) of the mouse (3-6), and Ir-5, which is located at a distance of 17 cm to the right of the H-2 complex on chromosome 17 (6). Previous genetic mapping with H-2 recombinant strains has indicated that the two Ir-Thy-1 loci are located to the left of the IC subregion (7). Further experiments strongly suggested that either one or both Ir-Thy-1 loci map to the K rather than the I region of the H-2 complex (8). In this report, the study of an H- 2 mutant, CBA-H-2(ka) (M523) (9), and its parental strain, CBA/LacStoY (CBA) provided further evidence that one of these loci apparently resides in the K region and might even be identical with the H-2K locus in that region.     

The maternal immune response to a new human trophoblast antigen

The trophoblast membrane of the human placenta constitutes the effective interface between blood borne cells of the maternal immune system and foetal tissue. Therefore antigens expressed on this membrane are ideally located to induce an immune response. We have previously described a trophoblast antigen TA which induces a humoral response. In this study the leucocyte migration inhibition assay was employed to assess the cellular response of pregnant women to TA. Leucocytes from primigravidae and multigravidae responded to TA while controls did not. Addition of autologous pregnancy sera abrogated responses to TA but did not affect responses to BCG. We propose that pregnancy sera contains a blocking factor which contributes to the survival of the foetal allograft by suppressing a potentially hostile maternal immune response directed against TA expressed on the trophoblast membrane.     

The immune response to the HPA-la antigen: association with HLA-DRw52a

Summary. Antibodies to the HPA-la antigen can elicit a condition in the new-born known as neonatal alloimmune thrombocytopenia (NAITP). Retrospective and prospective studies have shown that there is a strong correlation between the presence of HLA-DR3, HLA-DRw52 in the mother and the antibody response to HPA-la. HLA Class II molecules play an important role in the initiation of the immune response and it has been postulated that HPA-la antibody production could be determined by the presence of a specific HLA Class II molecule at the surface of the antigen-presenting cell. Thirty-one HPA-la negative women with HPA-la antibodies (responders) and nine HPA-la negative women without HPA-la antibodies (non-responders) were recruited. They were studied using serological HLA Class I and Class II typing and RFLP analysis with a DRβ probe. We found that all responders had the HLA-DRw52a sub-specificity confirming recently published data. Moreover, two of the nine non-responders were also found to be HLA-DRw52a. These results suggest that the HLA-DRw52a molecule is necessary for HPA-la antibody responsiveness but not sufficient. The results also indicate that in HPA-la negative women the absence of HLA-DRw52a is associated with a very low risk of being antibody producers and hence, is associated with a very low risk for NAITP in their new-borns.     

Cytotoxic T lymphocytes produce immune interferon in response to antigen or mitogen

Interferon (IFN) was found to be secreted by cloned lines of murine cytotoxic T lymphocytes in response to mitogenic or antigen specific stimulation. The IFN produced was shown to be of the immune type based on its sensitivity to pH 2.0 and on the ability of an antiserum to immune IFN to neutralize the antiviral activity.     

Pulmonary surfactant suppresses the immune lung injury response to inhaled antigen in guinea pigs

Pulmonary surfactant (PS) has been shown to regulate the function of macrophages, T cells, B cells, and NK cells in vitro. We designed this study to explore the immunoregulatory role of PS in vivo. Guinea pigs were immunized to complete Freund's adjuvant (CFA) and 2 weeks later were subjected to an aerosol challenge with purified protein derivative (PPD) to induce immune lung injury (group I). Group II and group III were subjected to lung lavage by tracheostomy just before aerosol challenge. Group II was lavaged with 0.9% NaCl, which depleted PS by 32%. Group III was lavaged with 0.9% NaCl containing bovine surfactant, which did not alter total PS content. Control animals for each condition were not presensitized to CFA. All guinea pigs were killed 24 hours after the aerosol challenge; for each group n = 10 +/- 2. Bronchoalveolar lavage (BAL) protein and mononuclear leukocyte counts, as well as lung histopathologic grading, were performed. Group I animals showed evidence of mild immune lung injury by these parameters. Animals partially depleted of PS (group II) showed more severe lung injury with greater abnormalities in BAL leukocytes and histopathology compared with group I. Guinea pigs lavaged with fluid containing bovine surfactant (group III) were nearly identical to group I with respect to these two parameters. BAL protein levels were not related to PS depletion. This study suggests that surfactant may have an in vivo role in modulating the inflammatory response that accompanies immune lung injury in this model.     

PAR-1 contributes to the innate immune response during viral infection

Coagulation is a host defense system that limits the spread of pathogens. Coagulation proteases, such as thrombin, also activate cells by cleaving PARs. In this study, we analyzed the role of PAR-1 in coxsackievirus B3–induced (CVB3-induced) myocarditis and influenza A infection. CVB3-infected Par1^–/– mice expressed reduced levels of IFN-β and CXCL10 during the early phase of infection compared with Par1^+/+ mice that resulted in higher viral loads and cardiac injury at day 8 after infection. Inhibition of either tissue factor or thrombin in WT mice also significantly increased CVB3 levels in the heart and cardiac injury compared with controls. BM transplantation experiments demonstrated that PAR-1 in nonhematopoietic cells protected mice from CVB3 infection. Transgenic mice overexpressing PAR-1 in cardiomyocytes had reduced CVB3-induced myocarditis. We found that cooperative signaling between PAR-1 and TLR3 in mouse cardiac fibroblasts enhanced activation of p38 and induction of IFN-β and CXCL10 expression. Par1^–/– mice also had decreased CXCL10 expression and increased viral levels in the lung after influenza A infection compared with Par1^+/+ mice. Our results indicate that the tissue factor/thrombin/PAR-1 pathway enhances IFN-β expression and contributes to the innate immune response during single-stranded RNA viral infection.     

Antigen recognition and the immune response. Humoral and cellular immune responses to small mono- and bifunctional antigen molecules

L-Tyrosine azobenzene-p-arsonate (RAT) induced cellular immunity without antibody production in guinea pigs. Bifunctional antigens were prepared consisting of one RAT carrier moiety linked either directly to a dinitrophenyl (DNP) haptenic determinant or through one or more 6-amino-caproyl (SAC) spacers. Each SAC unit has an extended span of 8 A. Guinea pigs immunized with these conjugates developed cellular immunity directed against the RAT determinant and antibody specific for the DNP determinant. The anti-DNP response was the same with one or three SAC spacers, but was significantly weaker when the two determinants were joined without a spacer. Animals immunized with either DNP-SAC-TYR or DNP-TYR developed neither cellular nor humoral immunity. Prior immunization with RAT potentiated the secondary anti-hapten response to DNP-SAC-RAT. Modification of RAT at either the arsonate or tyrosine positions showed that other charged groups (sulfonate and trimethylammonium) could substitute for arsonate without loss of immunogenicity. Removal of either the amino or carboxyl group from the side chain of tyrosine did not abolish immunogenicity, but immunogenicity was lost upon removal of both. Immunization with symmetrical bifunctional RAT-(SAC)_n-RAT and cyclo-(L-RAT-D-RAT) antigens led to cellular immunity but no anti-arsonate antibody, suggesting a barrier to "self-help." These compounds were also ineffective in inducing a secondary anti-arsonate response in animals primed with arsonate-BSA conjugates and RAT.     

The immune response to pneumococcal proteins during experimental human carriage

Colonization of the nasopharynx is the initial step in all infections caused by Streptococcus pneumoniae. The antibody response to carriage was examined in an experimental model of human colonization in healthy adults. Asymptomatic colonization was detected in 6/14 subjects and continued for up to 122 d. Susceptibility to carriage did not correlate with total serum immunoglobulin (Ig)G to the homotypic capsular polysaccharide. All of the colonized subjects, in contrast, developed a serum IgG and secretory IgA response to a 22 kD protein, whereas 7 of 8 subjects who did not become colonized had preexisting antibody to this protein. Analysis of the 22 kD protein identified it as the NH(2)-terminal region of pneumococcal surface protein A (PspA). Our findings provide evidence for the role of antibody to this protein fragment in preventing pneumococcal carriage by humans.     

Competition between concanavalin A-induced stimulatory and inhibitory effects in the in vitro immune response to antigen

Adoptively transferred carrier immune T cells interact with nonimmune T cells in recipients in a fashion which generates specific immunosuppression although both the immune and normal cells function quite well as helper cells when not admixed.     

Role of CD8 T-cell in immune response to tuberculosis-specific antigen in QuantiFERON-TB Gold Plus

Recent contacts with active TB (tuberculosis) patients were screened for latent tuberculosis infection (LTBI) because of their greater relative risk for developing active TB. QuantiFERON®-TB Gold Plus (QFT-Plus) offers two TB-specific antigen tubes (TB1 and TB2). TB1 elicits CD4 T-cell responses, and TB2 is designed to elicit both CD4 and CD8 T-cell responses. These mechanisms could be useful for estimating the role of CD8 T-cell immune responses to TB-specific antigens. To estimate the QFT-Plus capability to diagnose LTBI, a prospective cross-sectional study was conducted. A total of 412 TB contacts (median age 44 years) were enrolled. The positivity rates of QFT-Plus, TB1 and TB2 were 7.5%, 6.3% and 7.2%, respectively. TB2 showed a higher positivity rate compared to TB1, but without significant difference. The interferon (IFN)-γ productions of TB1 and TB2 were well correlated (r = 0.934, P < 0.001). The ratio of IFN-γ production between TB1 and TB2 showed a median (interquartile range) of IFN-γ_{[QFT-Plus TB2]}/IFN-γ_{[QFT-Plus TB1]} of 1.09 (0.91–1.36). CD8 T-cell immune response to TB-specific antigens varied among subjects. CD8 T-cell potentially boosts IFN-γ productions in QFT-Plus and results in the detection of more persons with LTBI. However, there was no significant difference in the positivity rates of QFT-Plus TB1 and TB2 in our TB contact investigation. The contribution of CD8 T-cells might be small for the diagnosis of LTBI. The analysis of IFN-γ production in both TB1 and TB2 would lead to further analysis of the TB immune response, and especially that caused by CD8 T-cells.     

Hepatitis B core antigen specific CD4 response in peripheral blood

The proliferative response of peripheral blood CD4+ T cells to recombinant hepatitis B core antigen (rHBcAg) has been studied in patients with chronic active hepatitis (CAH) type B (CAH-B), CAH-nonA nonB, and normal volunteers. CD4+ T cells from patients with CAH-B indicated a significant proliferative response to rHBcAg in the presence of non-T antigen presenting cells. In contrast, there was no apparent T cell reaction to rHBcAg in patients with CAH-nonA nonB and healthy volunteers. We suggested the possibility of CD4-mediated HBcAg specific response even in the peripheral blood compartments of HBcAg-responsive CAH-B patients.     

人HL-60白血病细胞混合抗原肽诱导特异性免疫应答的研究

目的：研究人HL－60白血病细胞混合抗原肽诱导特异性免疫应答的作用及其特异性。方法：用细胞冻融、加热沉淀及酸处理等方法除去HL－60细胞的核酸，脂质及大部分蛋白，制备混合抗原肽，体外将抗原肽与热休克蛋白70（Hsp70)结合，以T细胞体外激活试验检测结合物对人外周血单个核细胞（PBMNC）的刺激作用。并对激活的淋巴细胞进行传代培养，观察细胞的增殖；收集传代增殖的淋巴细胞，检测其对HL－60及K562白血病细胞的杀伤功能。结果：采用上述方法制备的抗原肽为混合肽，该混合肽经Hsp70提呈后，体外能激活PBMNC，并使激活的细胞增殖，增殖的淋巴细胞可特异性地杀伤HL－60细胞，但对K562细胞无杀伤作用。结论：白血病细胞内含有可用生化方法制备的特异性抗原肽；利用Hsp70提呈此抗原肽可知细胞毒性T淋巴细胞增殖，对白血病细胞产生特异的杀伤作用，对于化疗后防止血病复发将具有十分重要的意义。     

Negative selection,not receptor editing,is a physiological response of autoreactive thymocytes

Antigen receptor editing—a process of secondary rearrangements of antigen receptor genes in autoreactive lymphocytes—is a well-established tolerance mechanism in B cells, whereas its role in T cells remains controversial. Here, we investigated this issue using a novel Tcra knock-in locus, which ensured appropriate timing of TCRα expression and allowed secondary rearrangements. Under these conditions the only response to self-antigen that could be unambiguously identified was negative selection of CD4/CD8 double positive thymocytes. No evidence could be obtained for antigen-induced TCR editing, whereas replacement of the transgenic TCRα chain by ongoing gene rearrangement occurred in some cells irrespective of the presence or absence of self-antigen.The diversity of antigen receptors in the adaptive immune system of vertebrates is generated by a random recombinatorial process, and thus receptors recognizing self-antigens are constantly generated, creating a risk of autoimmunity. Therefore, the immune system requires an array of mechanisms to disarm autoreactive lymphocytes. This includes negative selection, induction of anergy, diversion to lineages with regulatory properties, and antigen receptor editing.Receptor editing is a process of secondary rearrangements of antigen receptor genes in response to recognition of self-antigen. This phenomenon is well described for B cells (Nemazee and Hogquist, 2003); however, its role in T cell tolerance remains controversial (Mostoslavsky and Alt, 2004), in part because of the lack of an appropriate mouse model. Indirect experiments using mice expressing TCR transgenes that were not contained within endogenous TCR loci suggested that editing may exist because T cells with receptors specific for peptide ligands expressed in the thymic cortex appeared to undergo rearrangements of the endogenous Tcra locus (McGargill et al., 2000). In this setting, endogenous TCRα chains have to compete with the transgenic TCRα for pairing with TCRβ chains. The varying efficiency of such competition for different TCR transgenes may explain the fact that OT-I, but not HY or 2C TCRs, allowed for the appearance of transgene-negative, TCR-positive cells in the presence of antigen (Mayerova and Hogquist, 2004). Other studies have suggested that editing may even take place after thymic egress and peripheral antigens could induce TCRβ rearrangements in peripheral T cells specific for these antigens (McMahan and Fink, 1998). More direct experiments in which a rearranged VαJα exon of the HY TCRα chain was knocked-in into the Tcra locus in a way that mimics the product of physiological VαJα rearrangement (HY-I mouse), and thus could be deleted by secondary rearrangements, indicated, however, an absence of TCR editing (Buch et al., 2002). Secondary rearrangements did occur to some extent in this system in the absence of the self-antigen, but were not increased in its presence. These secondary rearrangements, also observed in another Tcra knock-in system (Wang et al., 1998), are thought to be a mechanism that enhances the generation of TCRs suitable for positive selection in WT mice. Unexpectedly, however, the knock-in TCRα allele constructed by Buch et al. (2002) was expressed prematurely, in CD4/CD8 double-negative 3 (DN3) thymocytes (Croxford et al., 2008), whereas under physiological conditions Tcra is rearranged only at the CD4/CD8 double positive (DP) stage. Thus expression of the TCR in this system could occur too early, at a point in time when editing may not yet be possible. Indeed, rearrangement of antigen receptors takes place only in nonproliferating populations, as Rag2 is unstable in dividing cells (Li et al., 1996; Lee and Desiderio, 1999), whereas expression of the TCRβ chain in DN3 cells initiates a burst of proliferation that is likely to interfere with V(D)J recombination. Although, in B cells, premature expression of an autoreactive BCR does not interfere with editing, which still occurs after a wave of proliferation (Pelanda et al., 1997), similar rules do not have to apply to T cells. Moreover, premature TCRαβ expression is known to divert cells to γδ-like lineage (Bruno et al., 1996; Terrence et al., 2000; Baldwin et al., 2005; Egawa et al., 2008) and it is unclear whether that is compatible with editing. Some in vitro experiments were performed to address this issue, and appeared to contradict this possibility (Buch et al., 2002); however, this system did not allow tackling the issue properly in the in vivo setting. Thus, a model with correct timing of TCR expression is required to address the impact of TCRα editing under physiological conditions.A successful approach to correct the timing of TCRα transgene expression was developed by Baldwin et al. (2005). The authors placed a floxed STOP cassette between the promoter and the HY TCRα transgene, thus preventing premature TCRα expression. The STOP cassette was then excised by CD4-Cre that is expressed from the DP stage, ensuring proper timing of TCRα expression (HY^cd4 mouse). However, the transgene used could not be deleted by secondary rearrangements, and thus Tcra editing could not be addressed in this system. We adopted this approach to correct the timing of TCRα expression in the HY-I system. In the resulting HY-STOP mice, the onset of HY TCRα expression took place physiologically, at the DP stage. Correction of the timing of TCR expression rescued the abnormalities in the gross thymic phenotype observed in HY-I mice. However, no evidence for TCRα editing was found in this system, and autoreactive cells instead were eliminated by negative selection.     

Globin attenuates the innate immune response to endotoxin

Hemoglobin is an endotoxin (lipopolysaccharide; LPS)-binding protein that synergistically increases the release of proinflammatory cytokines from the innate immune system in response to LPS. It has been suggested that this activity of hemoglobin facilitates the recognition of Gram-negative bacteria in a wound, thereby maximizing immune efficiency. This synergy may be important to the pathogenesis of a broad spectrum of clinical conditions because elevated hemoglobin levels frequently are observed in patients after the transfusion of red cells, trauma, cardiopulmonary bypass surgery, hemolysis, in addition to other disorders. To determine the molecular basis of the specific hemoglobin-LPS synergy, in this article we tested the effects of globin itself on macrophage responses to LPS. Paradoxically, these studies revealed that globin suppressed tumor necrosis factor (TNF) synthesis in LPS-stimulated murine and human macrophage cultures. LPS comigrated with globin on non-denaturing electrophoretic gels, giving direct evidence for binding. Globin specifically inhibited LPS activity in the standard Limulus assay but did not inhibit interleukin-1beta-mediated TNF synthesis. Iron supplementation of macrophage cultures significantly increased interleukin-1beta-induced TNF release. Intraperitoneal administration of globin protected mice against both LPS-induced lethality and experimentally induced bacterial infection. Thus, the heme-iron moiety of hemoglobin, and not the binding of LPS to globin, enhanced macrophage responses to LPS.     

Innate immune response to adenovirus.

Adenovirus is a common infectious pathogen in both children and adults. It is a significant cause of morbidity in immunocompetent people living in crowded living conditions and of mortality in immunocompromised hosts. It has more recently become a popular vehicle for gene therapy applications. The host response to wild-type infection and gene therapy vector exposure involves both the innate and adaptive immune systems. The initial innate immune response is associated with the severe acute manifestations of adenovirus infection and also plays a significant role in acute toxicity owing to adenovirus vector exposure. This review discusses the innate immune response primarily during wild-type adenovirus infection because this serves as the basis for understanding the response during both natural infection and exposure to adenovirus vectors.