Lysis mediated by T cells and restricted by H-2 antigen of target cells infected with vaccinia virus

VARIOUS virus infections lead to the formation of cytotoxic lymphocytes (CL), which are capable of killing virus-infected target cells1−4. Specific lysis of target cells infected with 51Cr-labelled vaccinia virus could be observed when investigating the cell-mediated cytotoxic reaction to vaccinia virus5; the CL could be characterised as a T cell. The sensitised lymphocytes from C3H mice could only kill syngeneic L929 cells infected with vaccinia virus, whereas lysis by sensitised lymphocytes derived from DBA/2 mice was restricted to the syngeneic infected mastocytoma P815X2 cells. In the lymphocytic choriomeningitis infection the target cell lysis was shown to be restricted by H-2 antigen6. We report here experiments with primary fibroblasts of the mouse strains C3H, DBA/2 and the (C3H DBA/2)F1 generation were designed to affirm that the effector phase of virus-specific lysis of target cells mediated by T cells is restricted by H-2 antigen even in the vaccinia virus infection. Further experiments with H-2 alloantisera were performed to indicate the close local relationship between H-2 antigens and viral surface antigens

Low-level regulatory T-cell activity is essential for functional type-2 effector immunity to expel gastrointestinal helminths

Helminth infection is frequently associated with the expansion of regulatory T cells (Tregs) and suppression of immune responses to bystander antigens. We show that infection of mice with the chronic gastrointestinal helminth Heligmosomoides polygyrus drives rapid polyclonal expansion of Foxp3(+)Helios(+)CD4(+) thymic (t)Tregs in the lamina propria and mesenteric lymph nodes while Foxp3(+)Helios(-)CD4(+) peripheral (p)Treg expand more slowly. Notably, in partially resistant BALB/c mice parasite survival positively correlates with Foxp3(+)Helios(+)CD4(+) tTreg numbers. Boosting of Foxp3(+)Helios(+)CD4(+) tTreg populations by administration of recombinant interleukin-2 (rIL-2):anti-IL-2 (IL-2C) complex increased worm persistence by diminishing type-2 responsiveness in vivo, including suppression of alternatively activated macrophage and granulomatous responses at the sites of infection. IL-2C also increased innate lymphoid cell (ILC) numbers, indicating that Treg functions dominate over ILC effects in this setting. Surprisingly, complete removal of Tregs in transgenic Foxp3-DTR mice also resulted in increased worm burdens, with "immunological chaos" evident in high levels of the pro-inflammatory cytokines IL-6 and interferon-γ. In contrast, worm clearance could be induced by anti-CD25 antibody-mediated partial depletion of early Treg, alongside increased T helper type 2 responses and without incurring pathology. These findings highlight the overarching importance of the early Treg response to infection and the non-linear association between inflammation and the prevailing Treg frequency

Immune Evasion by Yersinia enterocolitica: Differential Targeting of Dendritic Cell Subpopulations In Vivo

CD4+ T cells are essential for the control of Yersinia enterocolitica (Ye) infection in mice. Ye can inhibit dendritic cell (DC) antigen uptake and degradation, maturation and subsequently T-cell activation in vitro. Here we investigated the effects of Ye infection on splenic DCs and T-cell proliferation in an experimental mouse infection model. We found that OVA-specific CD4+ T cells had a reduced potential to proliferate when stimulated with OVA after infection with Ye compared to control mice. Additionally, proliferation of OVA-specific CD4+ T cells was markedly reduced when cultured with splenic CD8α+ DCs from Ye infected mice in the presence of OVA. In contrast, T-cell proliferation was not impaired in cultures with CD4+ or CD4−CD8α− DCs isolated from Ye infected mice. However, OVA uptake and degradation as well as cytokine production were impaired in CD8α+ DCs, but not in CD4+ and CD4−CD8α− DCs after Ye infection. Pathogenicity factors (Yops) from Ye were most frequently injected into CD8α+ DCs, resulting in less MHC class II and CD86 expression than on non-injected CD8α+ DCs. Three days post infection with Ye the number of splenic CD8α+ and CD4+ DCs was reduced by 50% and 90%, respectively. The decreased number of DC subsets, which was dependent on TLR4 and TRIF signaling, was the result of a faster proliferation and suppressed de novo DC generation. Together, we show that Ye infection negatively regulates the stimulatory capacity of some but not all splenic DC subpopulations in vivo. This leads to differential antigen uptake and degradation, cytokine production, cell loss, and cell death rates in various DC subpopulations. The data suggest that these effects might be caused directly by injection of Yops into DCs and indirectly by affecting the homeostasis of CD4+ and CD8α+ DCs. These events may contribute to reduced T-cell proliferation and immune evasion of Ye

Peanut‐induced anaphylaxis in children and adolescents: Data from the European Anaphylaxis Registry

Background Peanut allergy has a rising prevalence in high-income countries, affecting 0.5%-1.4% of children. This study aimed to better understand peanut anaphylaxis in comparison to anaphylaxis to other food triggers in European children and adolescents. Methods Data was sourced from the European Anaphylaxis Registry via an online questionnaire, after in-depth review of food-induced anaphylaxis cases in a tertiary paediatric allergy centre. Results 3514 cases of food anaphylaxis were reported between July 2007 - March 2018, 56% in patients younger than 18 years. Peanut anaphylaxis was recorded in 459 children and adolescents (85% of all peanut anaphylaxis cases). Previous reactions (42% vs. 38%; p = .001), asthma comorbidity (47% vs. 35%; p < .001), relevant cofactors (29% vs. 22%; p = .004) and biphasic reactions (10% vs. 4%; p = .001) were more commonly reported in peanut anaphylaxis. Most cases were labelled as severe anaphylaxis (Ring&Messmer grade III 65% vs. 56% and grade IV 1.1% vs. 0.9%; p = .001). Self-administration of intramuscular adrenaline was low (17% vs. 15%), professional adrenaline administration was higher in non-peanut food anaphylaxis (34% vs. 26%; p = .003). Hospitalization was higher for peanut anaphylaxis (67% vs. 54%; p = .004). Conclusions The European Anaphylaxis Registry data confirmed peanut as one of the major causes of severe, potentially life-threatening allergic reactions in European children, with some characteristic features e.g., presence of asthma comorbidity and increased rate of biphasic reactions. Usage of intramuscular adrenaline as first-line treatment is low and needs to be improved. The Registry, designed as the largest database on anaphylaxis, allows continuous assessment of this condition

Localization of allodeterminants on H-2Kb antigens determined with monoclonal antibodies and H-2 mutant mice.

The topographic arrangement of antigenic determinants on the H-2Kb molecule was investigated by antibody competition studies with a series of monoclonal anti-Kb antibodies. For identification of amino acid residues participating in formation of allodeterminants H-2Kb mutant mice with defined amino acid substitutions were analyzed. The determinants were found to be located in at least two spatially separate clusters on the H-2Kb molecule. Determinants of one cluster are affected by mutations at amino acid positions 155 and 156, whereas determinants of a second cluster are modified by amino acid substitutions at positions 77 and 89. For a third cluster of determinants no relevant amino acid positions could be identified, but competition data indicate that this cluster is adjacent to the second one. The data suggest that the first two domains of H-2 antigens carry most allodeterminants

Ontogeny of murine B lymphocytes: sequence of B-cell differentiation from surface-immunoglobulin-negative precursors to plasma cells.

Among bone-marrow-derived (B) lymphocytes exist subpopulations of cells that can be induced to express the markers: surface immunoglobulin (Ig), the antigen associated with the immune response gene (Ia), and the receptor for the third complement component (CR). Inducible cells for the first two markers are found in bone marrow, and inducible cells for all three are in spleen. Experiments were designed to determine whether induction involves a single precursor cell population that on triggering with lipopolysaccharide expresses all three surface markers, or three separate precursor cell populations each of which expresses a single marker. Specific B cell subpopulations were eliminated by treatment with anti-Ig or anti-Ia and complement, or by rosette formation with erythrocytes-antibody-complement followed by differential centrifugation, and surviving cells were subsequently tested for inducibility of the three B cell markers. After anti-Ig cytolysis only Ig, but not Ia and CR, could be induced, implying that the Ia- and the CR-inducible cells are Ig+. Similarly, after anti-Ia cytolysis Ig and Ia but not CR could be induced. Thus, CR-inducible cells must have the Ig+Ia+ phenotype. Elimination of CR+ cells did not affect the induction of Ig, Ia, or CR from their precursors. None of the three elimination experiments affected the conversion of prothymocytes (Thy-1-) to thymocytes (Thy-1+). From these results we propose the hypothesis that the differentiation of B lymphocytes proceeds through at least four distinct stages characterized by the following phenotypes: Ig-Ia-CR- leads to Ig+Ia-CR- leads to Ig+Ia+CR- leads to Ig+Ia+CR+

Labelling of mouse alloantibody with tritiated DL-alanine

Radio-iodination is not a satisfactory method of labelling mouse antibody, which is peculiarly susceptible to destruction during the process of iodination. An alternative which causes very little loss of antibody is the attachment of a tritium-labelled amino acid to mouse γG by peptide linkage. This is accomplished by reaction of γG with DL-alanine N-carboxy anhydride under mild conditions. The method is applicable to estimation in vitro of the relative amounts of H-2 antibody absorbed by viable cells, and of the relative amounts of H-2 antigen on viable cells. Non-specific uptake is virtually eliminated by: (i) prior absorption of the labelled product in vivo, (ii) pre-incubation of the cells in 20 per cent foetal bovine serum and its inclusion in the suspending medium, and (iii) performance of absorption procedures in the cold