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Summary: Hepatitis B virus (HBV) infection causes a self‐limiting disease in most individuals. However, < 10% of infected subjects develop a chronic disease. Genetic host variability of polymorphic genes at the interface of innate and acquired immunity, such as killer immunoglobulin‐like receptors (KIR), their human leucocyte antigen (HLA) and IgG allotypes (GM), could explain this different clinical picture. We previously showed a protective role of the KIR2DL3 gene for the development of chronic hepatitis B (CHB), and a detrimental role of the KIR ligand groups, HLA‐A‐Bw4 and HLA‐C2. We have expanded the previous analysis genotyping patients for GM23 and GM3/17 allotypes. The comparison of the patients with CHB with those who resolved HBV infection showed that the presence of GM17 allele virtually eliminated the risk of developing CHB (OR, 0·03; 95% CI, 0·004–0·16; P < 0·0001). In addition, the combination of GM17, KIR2DL3, HLA‐A‐Bw4 and HLA‐C2 was highly sensitive to predict the outcome of HBV infection. [ABSTRACT FROM AUTHOR]

This paper investigates the Vβ usage of lymph node cells from mice immunized with TNP and of cell lines made from them. In cell lines stimulated weekly with TNP in vitro for 1 month, about 87% of the cells were Vβ8+ and further analysis showed that these cells were actually Vβ.2+. This was also true for the cells that proliferated in lymph nodes in response to TNP 4 days after primary immunization, i.e. proliferation occurred mainly in the Vβ+, and in particular in the Vβ8.2+, population while much less proliferation occurred when the Vβ8- or Vβ8.2- T-cell populations are used. This was not due to non-specific damage during separation, as the response to concanavalin A and alloantigen was intact. In a separate series of experiments, mice were acutely depleted of Vβ8+ T cells by treatment with F23.1 or a control monoclonal antibody (mAb) in vivo given before immunization. Treatment with the relevant mAb virtually abolished the response to TNP. In contrast, SJL mice, which lack the gone segment coding for the Vβ8 family and several other Vβ chains, made a normal proliferative and delayed-type hypersensitivity (DTH) response to TNP. This poses the problem, which may he important in the study of the T-cell repertoire, of why acute removal of Vβ8+ T cells, which are dominantly used in the response to TNP, does not allow T cells using other chains to substitute in the response, while the absence of this population over a long period of time, because of a deletion in the genome, allows the use of T cells hearing other Vβ chains. [ABSTRACT FROM AUTHOR]

Cells must control genes that are induced by virus infection to mitigate deleterious consequences of inflammation. We investigated the mechanisms whereby Keap1 moderates the transcription of genes that are induced by Sendai virus infection in mouse embryo fibroblasts (MEFs). Keap1−/− deletions increased the transcription of virus induced genes independently of Nrf2. Keap1 moderated early virus induced gene transcription. Virus infection induced Keap1 to bind Ifnb1, Tnf and Il6, and reduced Keap1 binding at Cdkn1a and Ccng1. Virus infection induced G9a‐GLP and NFκB p50 recruitment, and H3K9me2 deposition. Keap1−/− deletions eliminated G9a‐GLP and NFκB p50 recruitment, and H3K9me2 deposition, but they did not affect NFκB p65, IRF3 or cJun recruitment. G9a‐GLP inhibitors (BIX01294, MS012, BRD4770) enhanced virus induced gene transcription in MEFs with intact Keap1, but not in MEFs with Keap1−/− deletions. G9a‐GLP inhibitors augmented Keap1 binding to virus induced genes in infected MEFs, and to cell cycle genes in uninfected MEFs. G9a‐GLP inhibitors augmented NFκB subunit recruitment in MEFs with intact Keap1. G9a‐GLP inhibitors stabilized Keap1 retention in permeabilized MEFs. G9a‐GLP lysine methyltransferase activity was required for Keap1 to moderate transcription, and it moderated Keap1 binding to chromatin. The interdependent effects of Keap1 and G9a‐GLP on the recruitment of each other and on the moderation of virus induced gene transcription constitute a feedback circuit. Keap1 and the electrophile tBHQ reduced virus induced gene transcription through different mechanisms, and they regulated the recruitment of different NFκB subunits. Characterization of the mechanisms whereby Keap1, G9a‐GLP and NFκB p50 moderate virus induced gene transcription can facilitate the development of immunomodulatory agents. [ABSTRACT FROM AUTHOR]

Summary: During inflammation or tissue injury, pro‐inflammatory mediators attract migratory monocytes to inflammatory sites and monocyte‐to‐macrophage differentiation occurs to activate macrophages. We report here that PAQR11, a member of the progesterone and AdipoQ receptor family, regulates monocyte‐to‐macrophage differentiation in vitro and in vivo. Paqr11 gene was highly induced during monocyte‐to‐macrophage differentiation. Knockdown or deletion of Paqr11 inhibited monocyte differentiation but had little effect on macrophage polarization. Mechanistically, PAQR11 promoted cell survival as apoptosis was increased by Paqr11 knockdown or deletion. Activation of the MAPK signalling pathway was involved in the regulatory role of PAQR11 on monocyte differentiation and cell survival. C/EBPβ regulated the expression of Paqr11 at the transcriptional level. In mice, deletion of Paqr11 gene alleviated progression of collagen‐induced rheumatoid arthritis. Thus, these results provide strong evidence that PAQR11 has a function in monocyte‐to‐macrophage differentiation and such function is related to autoimmune disease in vivo. [ABSTRACT FROM AUTHOR]

Summary: When monocytes migrate from blood into tissues they differentiate into macrophage‐like cells. The outcome of this differentiation process is strongly influenced by the tissue environment, and the macrophages produced help control the immunological properties of the tissue. The process of monocyte–macrophage differentiation is therefore potentially attractive when seeking therapeutic targets to amplify or modulate the inflammatory response. Here we highlight recent research in this area, identifying the gene Paqr11 as an important factor in monocyte differentiation, and therefore an important potential target for reducing macrophage‐mediated inflammation in arthritis. [ABSTRACT FROM AUTHOR]

The killer cell immunoglobulin-like receptor (KIR) locus comprises a variable and rapidly evolving set of genes encoding multiple inhibitory and activating receptors. The activating receptors recently evolved from the inhibitory receptors and both bind HLA class I and probably also class I-like structures induced by viral infection. Although generally considered natural killer (NK) cell receptors, KIR are also expressed by a large fraction of effector memory T cells, which slowly accumulate during human life. These effector memory cells are functionally similar to NK cells, as they are immediate effector cells that are cytotoxic and produce IFN-γ. However, different rules apply to NK and T cells with respect to KIR expression and function. For example, KIR tend to modulate signals driven by the T-cell receptor (TCR) rather than to act independently, and use different signal transduction pathways to modulate only a subset of effector functions. The most important difference may lie in the rules governing tolerance: while NK cells with activating KIR binding self-HLA are hyporesponsive, the same is unlikely to apply to T cells. We argue that the expression of activating KIR on virus-specific T cells carrying TCR that weakly cross-react with autoantigens can unleash the autoreactive potential of these cells. This may be the case in rheumatoid arthritis, where cytomegalovirus-specific KIR2DS2+ T cells might cause vasculitis. Thus, the rapid evolution of activating KIR may have allowed for efficient NK-cell control of viruses, but may also have increased the risk that slowly evolving T-cell responses to persistent pathogens derail into autoimmunity. [ABSTRACT FROM AUTHOR]

DM catalyses class II-associated invariant chain peptide (CLIP) release, edits the repertoire of peptides bound to major histocompatibility complex (MHC) class II molecules, affects class II structure, and thereby modulates binding of conformation-sensitive anti-class II antibodies. Here, we investigate the ability of DM to enhance the cell surface binding of monomorphic antibodies. We show that this enhancement reflects increases in cell surface class II expression and total cellular abundance, but notably these effects are selective for particular alleles. Evidence from analysis of cellular class II levels after cycloheximide treatment and from pulse-chase experiments indicates that DM increases the half-life of affected alleles. Unexpectedly, the pulse-chase experiments also revealed an early effect of DM on assembly of these alleles. The allelically variant feature that correlates with susceptibility to these DM effects is low affinity for CLIP; DM-dependent changes in abundance are reduced by invariant chain (CLIP) mutants that enhance CLIP binding to class II. We found evidence that DM mediates rescue of peptide-receptive molecules from inactive forms in vitro and evidence suggesting that a similar process occurs in cells. Thus, multiple mechanisms, operating along the biosynthetic pathway of class II molecules, contribute to DM-mediated increases in the abundance of low-CLIP-affinity alleles. [ABSTRACT FROM AUTHOR]

We previously reported that Staphylococcus aureus avoids killing within macrophages by exploiting the action of Toll-like receptor 2 (TLR2), which leads to the c-Jun N-terminal kinase (JNK)-mediated inhibition of superoxide production. To search for bacterial components responsible for this event, a series of S. aureus mutants, in which the synthesis of the cell wall was interrupted, were screened for the level of JNK activation in macrophages. In addition to a mutant lacking the lipoproteins that have been suggested to act as a TLR2 ligand, two mutant strains were found to activate the phosphorylation of JNK to a lesser extent than the parental strain, and this defect was recovered by acquisition of the corresponding wild-type genes. Macrophages that had phagocytosed the mutant strains produced more superoxide than those engulfing the parental strain, and the mutant bacteria were more efficiently killed in macrophages than the parent. The genes mutated, dltA and tagO, encoded proteins involved in the synthesis ofd-alanylated wall teichoic acid. Unlike a cell wall fraction rich in lipoproteins,d-alanine-bound wall teichoic acid purified from the parent strain by itself did not activate JNK phosphorylation in macrophages. These results suggest that thed-alanylated wall teichoic acid of S. aureus modulates the cell wall milieu for lipoproteins so that they effectively serve as a ligand for TLR2. [ABSTRACT FROM AUTHOR]

The really interesting new gene (RING) finger ubiquitin ligase domain of the recombinase activating gene 1 (RAG1) V(D)J recombinase protein adopts a standard cross-brace architecture but co-ordinates three zinc ions as opposed to the canonical two. We demonstrated previously that disruption of the conserved zinc co-ordination sites resulted in loss of structural integrity and ubiquitin ligase (E3) activity and interfered with the ability of full-length RAG1 to support recombination. Here we present evidence that amino acids surrounding the third, non-canonical site also contribute to functional interaction with the ubiquitin conjugating (E2) enzyme CDC34, while certain residues on the RING domain’s surface important for interaction between other E2–E3 pairs are less critical to the functional RAG1–CDC34 interaction in this assay. Partial reduction of ubiquitin ligase activity was significantly correlated with reduction in the ability of RAG1 to support recombination of extra-chromosomal substrates ( r = 0·805, P = 0·009). While poly-ubiquitin chains could be generated, RAG1 did not promote rapid chain extension following mono-ubiquitylation of substrate, regardless of the E2 enzyme used. No single ubiquitin lysine mutant disrupted the ability of CDC34 to form ubiquitin chains on RAG1, and mass spectrometric analysis of the poly-ubiquitylated products indicated ubiquitin chain linkages through lysines 48 and 11. These data suggest that RAG1 promotes a mono-ubiquitylation reaction that is required for optimal levels of V(D)J recombination. [ABSTRACT FROM AUTHOR]

We studied the tolerization of neonatal thymocytes (NT), neonatal splenocytes (NS) and adult thymocytes (AT), transferred to syngeneic nude ( nu/nu) hosts previously injected with semi-allogeneic splenocytes, without any supportive immunosuppressive treatment. This protocol allows the study of peripheral tolerance in the absence of the thymus. BALB/c neonatal T cells and ATs were able to expand in syngeneic BALB/c nu/nu mice and functionally reconstituted an allogeneic response, rejecting (BALB/c × B6.Ba) F1 splenocytes transferred 3–4 weeks after injection of BALB/c cells. However, if (BALB/c × B6.Ba) F1 cells were injected into BALB/c nude hosts 30 days before transfer of NT, NS or AT cells, the F1 population was preserved and specific tolerance to B6 allografts was established. Furthermore, transfer to lymphopenic F1 nu/nu showed that tolerance could be established only for neonatal populations, showing that unique properties of neonatal T cells allow their tolerization in both lymphopenic and non-lymphopenic conditions, in the absence of suppressive immunotherapy. These results bring empirical support to the possibility of T-cell engraftment in immunodeficient patients showing partial identity with donor major histocompatibility complex (MHC) genes; the manipulation of immunological maturity of donor T cells may be the key for successful reconstitution of immunocompetence without induction of graft-versus-host disease. [ABSTRACT FROM AUTHOR]

Examples suggesting that all or part of the VH segment of a rearranged VHDJH may be replaced by all or part of another VH have been appearing since the 1980s. Evidence has been presented of two rather different types of replacement. One of these has gained acceptance and has now been clearly demonstrated to occur. The other, proposed more recently, has not yet gained general acceptance because the same effect can be produced by polymerase chain reaction artefact. We review both types of replacement including a critical examination of evidence for the latter. The first type involves RAG proteins and recombination signal sequences (RSS) and occurs in immature B cells. The second was also thought to be brought about by RAG proteins and RSS. However, it has been reported in hypermutating cells which are not thought to express RAG proteins but in which activation-induced cytidine deaminase (AID) has recently been shown to initiate homologous recombination. Re-examination of the published sequences reveals AID target sites in VH-VH junction regions and examples that resemble gene conversion. [ABSTRACT FROM AUTHOR]

The effects of macrophage chemotactic factor (MC F) and macrophage-activating factor (MAP) on protection to Listeria snonocytogenes were analysed using 'MCF-rich fraction' and murine recombinant interferon-gamma (rIFN-γ). Recombinant IFN-γ showed no macrophage chemotactlc activity in the assays performed in vitro and in vivo. Although a single injection of either MCF-rich fraction or rIFN-γ into the footpath of mice led to a significant degree of anti-listerial activity, the highest degree of protection was observed when injected together. The i.v. administration of 20,000 U rIFN-γ did not raise significant protective activity against Listeria; however, injection with rIFN-γ prior to that with the MCF-rich fraction into the footpad produced a higher level of protective activity than the group treated with MCF alone. In addiiton to MAF(IFN-γ), MCF seems to play another important role in the full expression of protection against L. monocytogenes. [ABSTRACT FROM AUTHOR]

The activities of two forms (7.5 and 5.5 S) of DNA ligase and of terminal deoxynucleotidyl transferase (TdT) have been studied in human thymocytes at different ages from 20 weeks pre-natal to 37 years after birth. Thymocytes have been selected on the basis of relative size and antigenicity (CD3, OKT3 immunofluorescence) with the cell sorter. For DNA ligases, three kinds of cells can be distinguished: (i) large antigenically negative cells of 20-week fetus, expressing only the 7.5 S enzyme; (ii) large antigenically positive cells without ligase activity; (iii) smaller antigenically positive cells, expressing only the 5.5 S enzyme. This last form of enzyme is found after birth. With respect to TdT expressed in OKT3- 5 μm cells and to OKT3+ thymocytes, it is observed that 5.5 S DNA ligase is found in a thymocyte population distinct from cells expressing TdT. Therefore, these results allow us to consider the 5.5 S DNA ligase activity as an additional functional marker for thymocyte maturation in humans. [ABSTRACT FROM AUTHOR]

The present study indicates that two Mab specific to Fc∊R (MabER) on human B lymphocytes also react with Fc∊R on macrophage and T-cell lines. More importantly, it is also shown that MabER cross-react with IgE-BFs derived from B, T and macrophage cell lines. This conclusion is supported by the following observations: (i) the binding of MabER to Fc∊R-bearing cells is blocked by the CSN of T, B and macrophage Fc∊R-bearing cell lines, known to contain IgE-BFs as shown by their inhibition of rosette formation between IgE-coated erythrocytes and Fc∊R-bearing cells; (ii) the material purified from the CSN of each Fc∊R( +) cell lines by affinity chromatography on MabER-Affi-gel blocks the rosetting of U937 cells with IgE but not with IgG-coated erythrocytes; (iii) the same affinity-purified material inhibits the binding of 125I-IgE to a selected anti-IgE Mab (Mab 75); and (iv) the CSN of Fc∊R( +) cells but not of Fc∊R(-) cells reacts in a solid-phase sandwich radioimmunoassay with two MabER (135-176). and their reactivity is significantly retained on IgE-Affi-gel from which it may be recovered by glycine elution. This RIA is not influenced by any class of Ig, including IgE, employed at a final concentration of 100 μg/ml. Human serum also reacts in the RIA, and parellel dilution curves are obtained with different CSN and human sera. The RIA proved to be a reproducible and sensitive method to quantify human IgE-BFs. The expression of the same antigenic determinants on Fc∊R from T, B and macrophages as well as on the IgE-BFs secreted by these cells indicates structural homology between IgE receptors and IgE-FBs and suggests that they are encoded by the same gene. [ABSTRACT FROM AUTHOR]

Purified, monocyte-derived interleukin-l (IL-l) was found to provide growth support for Epstein- Barr virus (EBV) transformed B-lymphocytes seeded at densities below which their own autostimulatory factors were limiting. By contrast, highly purified resting B cells triggered via their receptors for antigen failed to respond to identical preparations of IL-l by DNA synthesis. That successful priming of the B cells had occurred was evidenced by a transient rise in RNA synthesis and the ability of the cells to respond to T-cell supernatants by DNA synthesis. The findings indicate that while IL- l might perform an autostimulatory function in B lymphocyte proliferation it is not by itself sufficient to provide growth support for resting B cells activated through their receptors for antigen. The implications of these observations for autocrine models of B-cell growth are discussed. [ABSTRACT FROM AUTHOR]

Spleen cells from mice infected with Newcastle disease virus (NDV) fail to proliferate when cultured with allogeneic cells or with concanavalin A (Con A). This failure is not due to impairment of interleukin-l (IL- l) production or to a lack of accessory cell function as stimulator cells from NDV- infected mice induce DNA synthesis in the mixed lymphocyte reaction. However, spleen cells from NDV-infected mice fail to produce detectable amounts of interleukin-2 (IL-2) when stimulated with mitogenic doses of Con A and do not respond to exogenous IL-2-containing preparations. Furthermore, absorption experiments suggest that cells from NDV-infected mice fail to bind appreciable amounts of exogenous IL-2. All these events seem to be infection-dependent, as cells from mice injected with ultraviolet-inactivated NDV (UV-NDV) behave normally. [ABSTRACT FROM AUTHOR]

The genetic basis of guinea-pig leucocyte antigen (GPLA)-B.2-associated unresponsiveness in the guinea-pig mixed leucocyte culture (MLC) was investigated using fibroblasts as stimulating cells. Guinea-pig foetal fibroblasts bearing the B.2 specificity can stimulate allogeneic but not syngeneic lymph node lymphocytes, whereas B.2-bearing peritoneal exudate cells (PEC) induce specific unresponsiveness. The inhibition of the mixed leucocyte-fibroblast reaction is seen only when the alloantisera are directed against the stimulatory fibroblast rather than the responding lymph node lymphocytes. Furthermore, B.2-bearing fibroblasts, in contrast to B.2-bearing PEC, fail to elaborate MLC-suppressor factor. It appears therefore, that in guinea-pig fibroblasts there is an apparent issociation between major histocompatibility complex (MHC; in the region of the B locus) genes and the gene(s) coding for B.2-associated MLC suppressor cells and factor(s). [ABSTRACT FROM AUTHOR]

We have made several T-T hybridomas which secrete soluble factors capable of suppressing an in vitro antibody response to nitrophenol (NP), but not other unrelated antigens. These factors bind specifically to NP. and express determinants coded for in the I-J region of the mouse major histocompatibility complex. No determinants that cross-react with the constant regions of mouse immunoglobulins are present on the factors. Three sub-clones originating from the same initial culture well of hybridoma cells secrete factors which carry I-J determinants of different haplotypes. One clone expresses 14 determinants derived from the supppressor cell parent, another expresses I-J determinants derived from the tumour cell parent, and a third expresses both. This correlates exactly with I-J determinants expressed on the cell membrane, and suggests the participation of at least two genes in the determination of suppressor-factor structure. [ABSTRACT FROM AUTHOR]

The component of bovine serum (coagglutinogen) responsible for coagglutination of guinea-pig red cells has been shown to be C4, as anticipated from our previously reported findings on human serum. To effect coagglutination, the C4 needs to be aggregated by antibody; thereby probably increasing the avidity of the C4 for the receptors on guinea-pig red cells. The coagglutinating activity is lost if univalent Fab anti-C4 is used, but it can be restored by adding IgG antibody to the Fab. A procedure is described for producing antibody reagents to human or bovine C4 by injecting guineapigs with well-washed coagglutinated guinea-pig red cells. [ABSTRACT FROM AUTHOR]

Salmonella typhimurium appears to divide faster in the spleen of naturally susceptible BALB/c than in resistant (B10 × A/J)F1 mice. S. typhimurium M526 is an LT2 derivative lysogenic for a non-excluding P22 mutant which allows superinfection with a second, non-replicating, P22 phage so that the proportion of superinfected organisms halves at each division. The true in vivo division and death rates can be calculated from successive determinations of the proportion of superinfected organisms and the viable count. It was found that the division time was 286 h in BALB/c and 5.02 h in (B10 × A/J)F1 the death rate was low and actually greater in the susceptible BALB/c strain. These results suggest that the gene controlling in vivo salmonella net growth rate, which is very important in natural resistance to salmonella infection, acts very early by regulating the division rate, perhaps inside macrophages. The actual mechanism remains unknown. [ABSTRACT FROM AUTHOR]

A one-step haemolytic assay using cellular intermediates was used to determine C2 levels in 50 HLA-A25 and B18 positive blood donors and four families suspected to have the C2-deficiency gene. The method clearly discriminated between homozygous normals and heterozygous deficient individuals, and it was found that approx. 50% of individuals with the haplotype HLA-A25,B18 had low levels of functional C2. in the four families studied, the close linkage of the C2-deficiency gene and the haplotype HLA-A25,B18 was confirmed. Furthermore, the C2-deficiency gene was shown to be a silent or null allele at the structural. [ABSTRACT FROM AUTHOR]

We introduced κ light chain genes into pre-B cells to increase the surface μ HC expression, and established transfectants expressing mature type of B-cell receptors (BCR) on pre-B-cell surfaces. Since the cytoplasmic conformations of the reconstituted BCR and intrinsic pre-B-cell receptor (pre-BCR) are identical, they would be connected with the identical signal transduction pathways in pre-B cells. By using the transfectants, we revealed that the reconstituted BCR on pre-B cells was functionally equivalent to BCR on mature B cells in terms of the induction of intracellular Ca++ mobilization. However, we found that the signal-transduction pathways through BCR on pre-B cells were quantitatively different from those of BCR on mature B cells in two ways. First, cross-linkage of the reconstituted BCR on pre-B cells induced preferential tyrosine phosphorylation of p120 and pl00, which was not observed when BCR on mature B cells was cross-linked. Second, BCR in pre-B cells was physic, ally associated with a larger amount of phosphatidylinositol-3 kinase (PI-3K) than BCR in mature B cells in spite of the fact that both pre-B and B cells expressed a similar amount of PI-3K in cytoplasm. Signals through pre-BCR and BCR are known to cause distinct biological effects in B-cell development. The biochemical features in the downstream of reconstituted BCR on pre-B cells, which we revealed in this study, will be of help in understanding the mechanism of functional differences between pre-BCR and BCR. [ABSTRACT FROM AUTHOR]

To elucidate the molecular basis for the ability of antibodies encoded by the human VH26 heavy-chain variable region gene to react with diverse antigens, we have generated 34 hybridomas secreting chimaeric monoclonal antibodies (human μ heavy chain/mouse light chains) from transgenic mice. The transgenic mice carry an immunoglobulin minilocus containing the human VH26 gene, human DH and JH gene segments, and genes encoding the human Cμ region. The minilocus in these animals undergoes functional rearrangement resulting in the production of chimaeric antibodies in which human μ heavy chains utilizing the VH26 gene are paired with mouse κ or λ light chains. The hybridomas described in this study were generated from naive animals and were selected solely on the basis of human μ-chain expression. The antibodies described have covalently attached mouse light chains and are multimeric in structure. The binding properties of the antibodies were examined using a panel of both self- and foreign antigens using enzyme-linked immunosorbent assays, agglutination or radio-immunoprecipitation assays and immunofluorescence. Chimaeric immunoglobulins from 21 of the 34 hybridoma clones (61·7%) reacted with one or more antigens, of which 13 (38·2%) reacted with more than two antigens. These studies demonstrate that the VH26 gene, in combination with human DH and JH gene segments, and mouse light-chain genes, is able to encode antibodies with a wide range of ligand-binding specificities. These findings have important implications in the context of the possible origins of autoantibodies encoded by VH26 which may play a role in the pathogenesis of a number of autoimmune conditions. [ABSTRACT FROM AUTHOR]

Because the T-cell receptor (TCR) α-chain locus is known to lack allelic exclusion of rearrangements, and as a recent report revealed the existence of α-chain double expressers among normal human peripheral blood lymphocytes (PBL), the possible existence of TCR α-chain double expressers among mature routine T cells was examined. Although two-colour staining analysis of normal T-cell populations did not immediately reveal recognizable clusters of Vet double expressers, alternative/n vitro stimulations of normal murine T cells with antibodies to two different TCR Vα chains reproducibly induced TCR α-chain double-expresser lines. TCR complexes with different α-chains on such T cells were both shown to be functional. The cell lines were heterogeneous with respect to Vβ usage and the ratio of the expressed amounts of the two α-chains on the surface. The ratio of the two expressed α-chains was found to be very stable over a long period of time. These results are consistent with the earlier report on α-chain double expressers among human T cells and also show normal occurrence of TCR α-chain double expressers in routine T-cell populations. [ABSTRACT FROM AUTHOR]

Cyclosporin A (CsA) is reported to inhibit programmed cell death. We confirmed this by using T-celI hybridomas which are inducible to programmed cell death by activation with immobilized anti-CD3 antibody or with anti-Thy 1.2 antibody. Cell death and DNA fragmentation, characteristic features of programmed cell death, were almost completely blocked by CsA or FK506. To investigate whether CsA inhibits only the cell death through the signals via the TCR/CD3 complex or all of the programmed cell death induced by various reagents, we further established CD4+8+ thymic lymphomas which result in programmed cell death after activation with calcium ionophore, dexamethasone, cyclic AMP or anti-CD3 antibody. It was revealed that CsA could block only the cell death mediated by the TCR/CD3 complex. For the clarification of the site of action of CsA, Ca2+ influx and endocytosis of receptors after stimulation with anti-CD3 antibody were monitored in the presence of CsA, and no significant effects of CsA were observed. Furthermore, prevention of cell death was examined by adding CsA at various periods of time after initiation of culture. CsA was found to exert its effect even when added after 4 h of cultivation, and the kinetic pattern of suppression was similar to that of the suppressive effect on IL-2 production. These observations indicate that in the events of programmed cell death, the major site of action of CsA will not be the inhibition of the immediate membrane events after activation of the TCR/CD3 complex but rather the interference in the function of molecules that transmit signals between membrane events and the activation of genes in the nucleus. [ABSTRACT FROM AUTHOR]

A putative synthetic vaccine for foot-and-mouth disease (FMDVI5) has proved less successful in a host species, cattle, than predicted by results in a small-animal model. Possible reasons for this include non-recognition by T cells influenced by major histocompatibility complex (MHC)-linked immune response gene control. It is now possible to type for human leucocyte antigen (HLA) DR-like bovine MHC (BoLA) class II polymorphisms with a one-dimensional isoelectric focusing (IEF) technique. Using this method 14 unrelated cattle were selected with eight different BoLA class II IEF types. After immunization with FMDV15, 13 cattle generated a T-cell response to FMDV15. However, the fine specificity and magnitude of the response was related to BoLA class II type. The non-response by one animal and low response by two other animals were associated with two of the BoLA class II types. Response to the region 149-158 was immunodominant and animals which did not respond to this region had low responses to the whole peptide. Using FMDV-specific T-cell lines five BoLA class II types associated with responder animals were able to present FMDV15 in an MHC class II-restricted fashion, indicating that this peptide is capable of binding to different MHC class II molecules and may account for the broad response observed. The restriction patterns of the lines indicated that the IEF method does not distinguish all functional polymorphisms. At least two of the IEF-defined types could each be split into two distinct specificities and revealed that the three sets of animals with identical IEF types in fact expressed distinct restriction elements. [ABSTRACT FROM AUTHOR]

A new histocompatibility locus, H-4, in the first linkage group of the mouse, has been identified. The gene-order in this linkage group is H-1, c, p, with H-4 very close to p but its position relative to p undetermined. There is 8.5 ± 2.1 per cent crossing over between H-1 and c in the heterozygous female, 5.4 ± 3.7 per cent in the heterozygous male. At least 4 alleles at the H-1 locus have been identified. The distribution of H-1 alleles in various inbred and co-isogenic resistant stocks is shown in Table 11. The mean survival of skin grafts made between various co-isogenic strain pairs, differing at H-1, ranges from 32 to 91 days, with a minimum survival of individual grafts of 20 days and a maximum of 124 days. Ovarian grafts between the same strain pairs show much longer survival. The significance of these results for estimates of gene numbers is discussed; the higher published estimates are favoured. [ABSTRACT FROM AUTHOR]

Stimulation of DNA synthesis by a guinea-pig albumin-orthanilic acid conjugate (AO) and by tuberculin purified protein derivative (PPD) was obtained in in vitro cultures of peripheral blood and lymph node lymphocytes from guinea- pigs with delayed hypersensitivity to these antigens. Animals sensitized to both AO and PPD were given further injection of 5 μ AO, intravenously, 8 hours before killing for in vitro studies. In these guinea-pigs, peripheral blood culture, but not lymph node cultures, showed greater DNA synthesis in response to both AO and PPD than cultures from controls not given a further injection of AO. It is suggested that the further increase in DNA synthesis was due to non-specific lymphocyte `activation' following the interaction of antigen and specifically sensitized lymphocytes. [ABSTRACT FROM AUTHOR]

Some antiallotype sera are found to be specific for allotypic determinants on two genetically closely linked categories of IgG globulins in the rabbit. Genetic and immunological evidence presented indicate that these two categories are two different IgG classes differing by their A chains. These have been called IgG1, defined by allotypic specificity As1 or its alleles, and IgG2, defined by allotypic specificity As8 or its alleles. Anti-DNP antibodies were shown to be present in both classes. A comparison with known allotypes in man, mouse and rabbit suggest that the structural genes for the A chains of the immunoglobulins are clustered together in a small chromosome region. [ABSTRACT FROM AUTHOR]

The proposition that single Vα or Vβ gene segments specify the recognition of the allele-specific determinants expressed on the major histocompatibility complex-encoded restricting elements of the species has as its consequence a totally different picture of the functioning of the T-cell receptor. This commentary justifies this assumption and outlines some of its most important consequences. [ABSTRACT FROM AUTHOR]

Summary Within the human T-cell receptor δ (TCRD ) gene we have identified a new cluster of seven δ recombining elements (δRec2.1–2.7), located 2·6–5·2 kilobases downstream of the Vδ2 gene segment. The δRec2 elements are isolated recombining signal sequences (RSS), which were shown to rearrange with the Dδ3 and Jδ1 segments of the TCRD gene as well as with the ψJα of the TCRA gene. Rearrangements involving the δRec2 elements were found in all peripheral blood (PB) samples from 10 healthy individuals, although their frequency was about 100-fold lower than that of classical δRec rearrangements. The total frequency of δRec2 rearrangements was lower in PB T lymphocytes, as compared with thymocytes, suggesting that they are deleted during T-cell development. The decrease of the frequency of the δRec2-Dδ3 rearrangements was most prominent: 11 times lower in PB T lymphocytes than in thymocytes. Since the δRec2-Jδ1 rearrangements contained the Dδ3 segment in the junctional region, we assume that they are derived from the δRec2-Dδ3 rearrangements. In contrast, the majority of δRec2-ψJα rearrangements did not contain the Dδ3 segment, indicating that they are single step rearrangements. The δRec2-Jδ1 and δRec2-ψJα rearrangements seem to be T-lineage specific, but the δRec2-Dδ3 rearrangements were also found at very low frequencies in B lymphocytes and natural killer cells. Our results suggest that δRec2 rearrangements are transient steps in the recombinatorial process of the TCRAD locus and are probably deleted by subsequent Vα-Jα rearrangements. We hypothesize, that in a similar manner to the classical δRec rearrangements, the δRec2 rearrangements might also contribute to T-cell differentiation towards the TCR-αβ lineage. [ABSTRACT FROM AUTHOR]