The reduction behavior of sulfurized polyacrylonitrile (SPAN) in lithium-sulfur batteries using a carbonate electrolyte: a computational study

Lithium-sulfur batteries (LSBs) have attracted attention due to their high theoretical energy density. This and various other advantages, such as the availability and non-toxicity of sulfur, raise interest in LSBs against the background of the energy revolution. However, a polysulfide shuttle mechanism can adversely affect the electrochemical performance of the cell. The sulfur redox properties are influenced, for example, by the electrolyte and the cathode material. Here, a computational study of the discharge process of an LSB with sulfurized poly(acrylonitrile) (SPAN) as the cathode material in combination with a carbonate electrolyte is presented. The nucleation of produced solid Li2S is compared to soluble Li2S. Dominating species are determined by comparing the Gibbs free energy of several species. We found that multiple lithiation steps occur before each Li2S detachment, preventing longer-chain polysulfide cleavage and a polysulfide shuttle. Through nucleating on the nitrogen-rich backbone of SPAN, Li2S units are stabilized by interactions with each other and with the nitrogen atoms. Experimental data show a potential drop and plateau during discharge, which is consistent with the calculated discharge profiles of SPAN with both soluble and nucleated Li2S, and hints at a direct solid-solid transition in the Li-SPAN cell during discharge when using carbonate-based electrolytes.

Generation of functional human thymic cells from induced pluripotent stem cells

BACKGROUND

The thymus is a glandular organ that is essential for the formation of the adaptive immune system by educating developing T cells. The thymus is most active during childhood and involutes around the time of adolescence, resulting in a severe reduction or absence of naive T-cell output. The ability to generate a patient-derived human thymus would provide an attractive research platform and enable the development of novel cell therapies.

OBJECTIVES

This study sought to systematically evaluate signaling pathways to develop a refined direct differentiation protocol that generates patient-derived thymic epithelial progenitor cells from multiple induced pluripotent stem cells (iPSCs) that can further differentiate into functional patient-derived thymic epithelial cells on transplantation into athymic nude mice.

METHODS

Directed differentiation of iPSC generated TEPs that were transplanted into nude mice. Between 14 and 19 weeks posttransplantation, grafts were removed and analyzed by flow cytometry, quantitative PCR, bulk RNA sequencing, and single-cell RNA sequencing for markers of thymic-cell and T-cell development.

RESULTS

A direct differentiation protocol that allows the generation of patient-derived thymic epithelial progenitor cells from multiple iPSC lines is described. On transplantation into athymic nude mice, patient-derived thymic epithelial progenitor cells further differentiate into functional patient-derived thymic epithelial cells that can facilitate the development of T cells. Single-cell RNA sequencing analysis of iPSC-derived grafts shows characteristic thymic subpopulations and patient-derived thymic epithelial cell populations that are indistinguishable from TECs present in primary neonatal thymus tissue.

CONCLUSIONS

These findings provide important insights and resources for researchers focusing on human thymus biology.

Predisposition to Proinsulin Misfolding as a Genetic Risk to Diet-Induced Diabetes

Throughout evolution, proinsulin has exhibited significant sequence variation in both C-peptide and insulin moieties. As the proinsulin coding sequence evolves, the gene product continues to be under selection pressure both for ultimate insulin bioactivity and for the ability of proinsulin to be folded for export through the secretory pathway of pancreatic β-cells. The substitution proinsulin-R(B22)E is known to yield a bioactive insulin, although R(B22)Q has been reported as a mutation that falls within the spectrum of mutant INS-gene-induced diabetes of youth. Here, we have studied mice expressing heterozygous (or homozygous) proinsulin-R(B22)E knocked into the Ins2 locus. Neither females nor males bearing the heterozygous mutation developed diabetes at any age examined, but subtle evidence of increased proinsulin misfolding in the endoplasmic reticulum is demonstrable in isolated islets from the heterozygotes. Moreover, males have indications of glucose intolerance, and within a few weeks of exposure to a high-fat diet, they developed frank diabetes. Diabetes was more severe in homozygotes, and the development of disease paralleled a progressive heterogeneity of β-cells with increasing fractions of proinsulin-rich/insulin-poor cells as well as glucagon-positive cells. Evidently, subthreshold predisposition to proinsulin misfolding can go undetected but provides genetic susceptibility to diet-induced β-cell failure.

The Lambda variant of SARS-CoV-2 has a better chance than the Delta variant to escape vaccines

The newly emerging variants of SARS-CoV-2 from India (Delta variant) and South America (Lambda variant) have led to a higher infection rate of either vaccinated or unvaccinated people. We found that sera from Pfizer-BioNTech vaccine remain high reactivity toward the receptor binding domain (RBD) of Delta variant while it drops dramatically toward that of Lambda variant. Interestingly, the overall titer of antibodies of Pfizer-BioNTech vaccinated individuals drops 3-fold after 6 months, which could be one of major reasons for breakthrough infections, emphasizing the importance of potential third boost shot. While a therapeutic antibody, Bamlanivimab, decreases binding affinity to Delta variant by ~20 fold, it fully lost binding to Lambda variant. Structural modeling of complexes of RBD with human receptor, Angiotensin Converting Enzyme 2 (ACE2), and Bamlanivimab suggest the potential basis of the change of binding. The data suggest possible danger and a potential surge of Lambda variant in near future.

Neurologisches Ergebnis und allgemeiner Gesundheitszustand bei Langzeitüberleben nach außerklinischer kardiopulmonaler Reanimation

Fragestellung

Für Deutschland liegen nur wenige Daten zum Gesundheitszustand und Langzeitüberleben nach außerklinischer Reanimation vor. Die vorliegende Studie untersucht den allgemeinen Gesundheitszustand und das neurologische Langzeitergebnis 2,5 bis 5 Jahre nach dem Reanimationsereignis sowie den Zusammenhang zwischen Behandlungsergebnis und präklinischen Patienten- und Behandlungsfaktoren.

Methodik

Alle über einen Zeitraum von 30 Monaten (2011–2013) durch den Rettungsdienst der Stadt Bonn durchgeführten Reanimationen wurden auf Grundlage der Notarzteinsatzprotokolle und des Deutschen Reanimationsregisters retrospektiv analysiert. Der allgemeine Gesundheitszustand wurde in Anlehnung an den SF-12 erfasst und das neurologische Langzeitergebnis kategorisiert (Cerebral Performance Category [CPC]). Die vorliegenden Daten wurden einer uni- und multivariaten logistischen Regressionsanalyse unterzogen.

Ergebnis

Von insgesamt 458 Patienten überlebten 17,9 % bis zur Krankenhausentlassung, 13,8 % mehr als 2,5 Jahre und 7,7 % bis zum Stichtag der Befragung. Von den noch lebenden Patienten hatten 85,3 % ein gutes neurologisches Ergebnis (CPC ≤ 2), welches durch ein geringeres Alter, einen beobachteten Kollaps, die Durchführung einer Defibrillation und das Ausbleiben einer Vasopressorgabe begünstigt wurde (multivariate Analyse). 74,2 % der Überlebenden beschrieben ihren Gesundheitszustand als gut.

Interpretation

Insgesamt überleben langfristig nur wenige Patienten einen außerklinischen Herz-Kreislauf-Stillstand. Die überlebenden Patienten beurteilen ihren Gesundheitszustand als gut und zeigen ein gutes neurologisches Ergebnis. Dabei hängt dieses Behandlungsergebnis von denselben Parametern wie der primäre Reanimationserfolg (Überleben bis Krankenhausaufnahme) ab. Die Etablierung klinischer Instrumente zur frühen Prognoseerstellung ist wünschenswert. Hierzu sind weitere Langzeituntersuchungen größerer Patientenkollektive mit Zugriff auf Routinedaten notwendig.

501Y.V2 and 501Y.V3 variants of SARS-CoV-2 lose binding to bamlanivimab in vitro

The newly emerging variants of SARS-CoV-2 from South Africa (B.1.351/501Y.V2) and Brazil (P.1/501Y.V3) have led to a higher infection rate and reinfection of COVID-19 patients. We found that the mutations K417N, E484K, and N501Y within the receptor-binding domains (RBDs) of the virus could confer ~2-fold higher binding affinity to the human receptor, angiotensin converting enzyme 2 (ACE2), compared to the wildtype RBD. The mutated version of RBD also completely abolishes the binding of bamlanivimab, a therapeutic antibody, in vitro. Detailed analysis shows that the ~10-fold gain of binding affinity between ACE2 and Y501-RBD, which also exits in the high contagious variant B.1.1.7/501Y.V1 from the United Kingdom, is compromised by additional introduction of the K417/N/T mutation. Mutation of E484K leads to the loss of bamlanivimab binding to RBD, although this mutation does not affect the binding between RBD and ACE2.

501Y.V2 and 501Y.V3 variants of SARS-CoV-2 lose binding to Bamlanivimab in vitro

We generated several versions of the receptor binding domain (RBD) of the Spike protein with mutations existing within newly emerging variants from South Africa and Brazil. We found that the mutant RBD with K417N, E484K, and N501Y exchanges has higher binding affinity to the human receptor compared to the wildtype RBD. This mutated version of RBD also completely abolishes the binding to a therapeutic antibody, Bamlanivimab, in vitro .

The basis of a more contagious 501Y.V1 variant of SARS-COV-2

Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) is causing a world-wide pandemic. A variant of SARS-COV-2 (20I/501Y.V1) recently discovered in the United Kingdom has a single mutation from N501 to Y501 within the receptor binding domain (Y501-RBD), of the Spike protein of the virus. This variant is much more contagious than the original version (N501-RBD). We found that this mutated version of RBD binds to human Angiotensin Converting Enzyme 2 (ACE2) a ~10 times more tightly than the native version (N501-RBD). Modeling analysis showed that the N501Y mutation would allow a potential aromatic ring-ring interaction and an additional hydrogen bond between the RBD and ACE2. However, sera from individuals immunized with the Pfizer-BioNTech vaccine still efficiently block the binding of Y501-RBD to ACE2 though with a slight compromised manner by comparison with their ability to inhibit binding to ACE2 of N501-RBD. This may raise the concern whether therapeutic anti-RBD antibodies used to treat COVID-19 patients are still efficacious. Nevertheless, a therapeutic antibody, Bamlanivimab, still binds to the Y501-RBD as efficiently as its binds to N501-RBD.

Lysosomal Protease Creation of Chimeric Epitopes for Diabetogenic CD4 T cells via Transpeptidation

The identification of the peptide epitopes presented by major histocompatibility complex class II molecules (MHCII) that drive the CD4 T cell component of autoimmune diseases has presented a formidable challenge over several decades. In type-1 diabetes (T1D) recent insight into this problem has come from the realization that several of the important epitopes are not directly processed from a protein source, but rather pieced together by fusion of different peptide fragments to create new chimeric epitopes. We have proposed that this fusion is performed by a reverse proteolysis reaction called transpeptidation, occurring during the catabolic turnover of pancreatic proteins when secretory granules fuse with lysosomes. Here we demonstrate that highly antigenic chimeric epitopes for diabetogenic CD4 T cells are produced by digestion of the appropriate fragments of the diabetogenic granule proteins with the lysosomal protease, cathepsin L (CatL). This pathway has implications for how self-tolerance can be broken in T1D and other autoimmune diseases.

JMJD6 cleaves MePCE to release positive transcription elongation factor b (P-TEFb) in higher eukaryotes

More than 30% of genes in higher eukaryotes are regulated by promoter-proximal pausing of RNA polymerase II (Pol II). Phosphorylation of Pol II CTD by positive transcription elongation factor b (P-TEFb) is a necessary precursor event that enables productive transcription elongation. The exact mechanism on how the sequestered P-TEFb is released from the 7SK snRNP complex and recruited to Pol II CTD remains unknown. In this report, we utilize mouse and human models to reveal methylphosphate capping enzyme (MePCE), a core component of the 7SK snRNP complex, as the cognate substrate for Jumonji domain-containing 6 (JMJD6)’s novel proteolytic function. Our evidences consist of a crystal structure of JMJD6 bound to methyl-arginine, enzymatic assays of JMJD6 cleaving MePCE in vivo and in vitro, binding assays, and downstream effects of Jmjd6 knockout and overexpression on Pol II CTD phosphorylation. We propose that JMJD6 assists bromodomain containing 4 (BRD4) to recruit P-TEFb to Pol II CTD by disrupting the 7SK snRNP complex.

In animals, an enzyme known as RNA polymerase II (Pol II for short) is a key element of the transcription process, whereby the genetic information contained in DNA is turned into messenger RNA molecules in the cells, which can then be translated to proteins. To perform this task, Pol II needs to be activated by a complex of proteins called P-TEFb; however, P-TEFb is usually found in an inactive form held by another group of proteins. Yet, it is unclear how P-TEFb is released and allowed to activate Pol II.

Scientists have speculated that another protein called JMJD6 (Jumonji domain-containing 6) is important for P-TEFb to activate Pol II. Various roles for JMJD6 have been proposed, but its exact purpose remains unclear. Recently, two enzymes closely related to JMJD6 were found to be able to make precise cuts in other proteins; Lee, Liu et al. therefore wanted to test whether this is also true of JMJD6. Experiments using purified JMJD6 showed that it could make a cut in an enzyme called MePCE, which belongs to the group of proteins that hold P-TEFb in its inactive form.

Lee, Liu et al. then tested the relationships between these proteins in living human and mouse cells. The levels of activated Pol II were lower in cells without JMJD6 and higher in those without MePCE. Together, the results suggest that JMJD6 cuts MePCE to release P-TEFb, which then activates Pol II. JMJD6 appears to know where to cut by following a specific pattern of elements in the structure of MePCE. When MePCE was mutated so that the pattern changed, JMJD6 was unable to cut it. These results suggest that JMJD6 and related enzymes belong to a new family of proteases, the molecular scissors that can cleave other proteins.

The molecules that regulate transcription often are major drug targets, for example in the fight against cancer. Ultimately, understanding the role of JMJD6 might help to identify new avenues for cancer drug development.

Synthesis, spectroscopic characterisation and transmetalation of lithium and potassium diaminophosphanide-boranes

A secondary diaminophosphane-borane (Et₂N)₂PH(BH₃) was prepared from a chlorophosphane precursor and LiBH₄ and metalated by reaction with anion bases (n-BuLi, KN(SiMe₃)₂) to yield the corresponding metal diaminophosphanide-boranes [(Et₂N)₂P(BH₃)]M (M = Li, K). Multinuclear NMR studies permitted the first spectroscopic characterisation of the metalation products and revealed the presence of monomeric (for M = Li) contact ion pairs in solution. NMR spectroscopic evidence that the ions in each pair interact via LiP- rather than LiH₃B-interactions as had been inferred for a Ph-substituted analogue was confirmed by DFT studies, which revealed also that the borane coordination plays a decisive role in boosting the PH-acidity of the original secondary diaminophosphane precursor. Transmetalation of the potassium and lithium diaminophosphanide-boranes with Cu(i) and Zn(ii) chlorides afforded the first functional transition metal complexes of a P-heteroatom-functionalised phosphanide-borane ligand. Both products were fully characterised. Thermolysis of the Cu-complex induced a reaction which involved transfer of an NHC ligand from the metal to the phosphorus atom and yielded a phosphaalkene NHC[double bond, length as m-dash]PH (NHC = N-heterocyclic carbene) as the major phosphorus-containing product.

The somatically generated portion of T cell receptor CDR3α contributes to the MHC allele specificity of the T cell receptor

Mature T cells bearing αβ T cell receptors react with foreign antigens bound to alleles of major histocompatibility complex proteins (MHC) that they were exposed to during their development in the thymus, a phenomenon known as positive selection. The structural basis for positive selection has long been debated. Here, using mice expressing one of two different T cell receptor β chains and various MHC alleles, we show that positive selection-induced MHC bias of T cell receptors is affected both by the germline encoded elements of the T cell receptor α and β chain and, surprisingly, dramatically affected by the non germ line encoded portions of CDR3 of the T cell receptor α chain. Thus, in addition to determining specificity for antigen, the non germline encoded elements of T cell receptors may help the proteins cope with the extremely polymorphic nature of major histocompatibility complex products within the species.

CD11c-expressing B cells from aged and autoimmune mice localize at T cell B cell border in spleen and present antigen more efficiently than Follicular B cells (BA3P.104)

Besides secretion of antigen-specific antibodies, B cells may play an important role in the generation of immune responses by efficiently presenting antigen to T cells. We and others recently described a subpopulation of CD11c+ B cells (Age/autoimmune associated B cells, ABCs) which appear with age, during virus infections and at the onset of some autoimmune diseases and which participate in autoimmune responses by secreting autoantibodies. Here we assessed the ability of these cells to present antigen and activate antigen-specific T cells. We demonstrated that ABCs present antigen to T cells, in vitro and in vivo, better than follicular B cells (FO cells) do. Our data indicate that ABCs express higher levels of the chemokine receptor, CCR7, and have higher responsiveness to CCL21 and CCL19 than FO cells and are localized at T/B cell border in spleen. Using multiphoton microscopy we have shown that in vivo, CD11c+ B cells form significantly more stable interactions with T cells than Follicular B cells. Together these data identify a previously undescribed role for ABCs as potent antigen-presenting cells and suggest another potential mechanism by which these cells can influence immune responses and/or the development of autoimmunity.

Paradigm-violating HLA class II-restricted CD8 T cells exist in HIV infected individuals (VIR6P.1164)

The T cell paradigm dictates that CD8 T cells recognize peptides presented by MHC class I. Yet, class II-restricted CD8 T cells were recently observed in rhesus macaques vaccinated with a RhCMV/SIV vector (reviewed in Ranasinghe and Walker 2013 Nat Biotech). Restriction of CD8 T cells by class II is rare, with less than a dozen published studies in two decades. Our study aimed to assess whether class II-restricted CD8 T cell responses exist in HIV infection. We detected class II-restricted CD8 T cells in 3 HIV infected individuals. The responses were identified using a novel 'HLA-DRB1 ELISpot' where patient CD8 T cells were co-cultured with HIV peptide-pulsed mouse LCL expressing human recombinant DRB1 (N=2/30 DRB1*01 and N=1/22 DRB1*11 subjects). Antibody blocking of class I and II, and class II tetramer binding confirmed the DRB1 restriction. Strikingly, up to 12% of total CD8 T cells bound class II tetramer directly ex vivo. The class II-restricted CD8αβ T cells expressed a TEMRA phenotype with a distinct polyfunctional profile and single TCR vBeta clonotype when compared intra-patient to class I-restricted CD8 TEM responses. Class II-restricted CD8 T cells exhibited high levels of Perforin and Granzyme B and efficiently lysed peptide-pulsed autologous BCL and CD4 T cells, yet showed impaired killing of autologous HIV-infected CD4 T cells in vitro. In our study, we have demonstrated the first proof-of-principle detection of class II-restricted HIV-specific CD8 T cells.

Characterizing the T cell receptor clonotype repertoire of an atypical HLA class II-restricted CD8 T cell response in HIV-1 infection (VIR6P.1170)

CD8 T cells targeting peptides presented by human leukocyte antigen (HLA) class II are atypical. Little is known about how the CD8 T cell receptor (TCR) recognizes peptides on HLA class II. We analyzed the TCR repertoire of a class II-restricted CD8 T cells targeting a HIV peptide. We identified an atypical HIV-specific CD8 response to DV16 peptide on HLA-DRB1*11. We sequenced the TCR of the class II-tetramer sorted cells. To measure the binding kinetics of the TCR with the peptide-MHC we used surface plasmon resonance (SPR). Analysis of 68 sequences showed that TCR-beta repertoire has a single TRBV2*01 clonotype. We looked at 64 sequences of TCRalpha and found that the repertoire had two clonotypes: TRAV26-1*02 and TRAV6*02. SPR revealed that only the TRAV6 was able to bind to the peptide-MHC. We studied 27 sequences of the CD4 T cells targeting the same MHC class II-peptide. We observed a polyclonal response of 16 clonotypes. 13 clonotypes used the same TRBV2*01 gene but had different rearrangements. Interestingly, two of these sequences are exactly the same as the dominant clonotype from the CD8 response. We found that the TCR is shared between CD8 and CD4 T cells targeting the same class II HLA-peptide. These data suggest that atypical CD8 cells express two different TCR alpha, possibly due to inefficient allelic exclusion during development. The use of the same TRBV2*01 by different CD4 clonotypes may suggest an atypical docking of TCR in the binding with peptide-HLA.

T-bet: a key player in a novel type of B cell activation essential for effective viral clearance (P4333)

IgG2a is known to be the most efficient antibody isotype for viral clearance. Here we demonstrate a novel pathway of B cell activation, leading to IgG2a production, and involving synergistic stimulation via B cell antigen receptors, TLR7 and interferon-gamma receptors. This leads to induction of T-bet expression in B cells, driving their differentiation into age-associated B cells (ABCs). T-bet positive ABCs appear during anti-viral responses and produce high titers of anti-viral IgG2a antibodies which are critical for efficient viral clearance. The results thus demonstrate a previously unknown role for T-bet expression in B cells during viral infections. Moreover the appearance of ABCs during anti-viral responses and during autoimmunity suggests a possible link between these two processes.

Characterizing the T cell receptor repertoire of beryllium-responsive CD4+ T cells (P5021)

Multiple public T cell receptor (TCR) repertoires exist in CD4+ T cells derived from the lung of patients with chronic beryllium disease (CBD). Here, we characterize the TCR Vβ5 repertoire which involves expression of a conserved glutamine (Q)-containing motif that is essential for TCR recognition of HLA-DP2/peptide/Be2+. Using a panel of human TCR Vβ antibodies, we show that beryllium-responsive, Vβ5.1+CD4+ T cell expansions exist in all DP2+ CBD patients tested to date. Sequence analyses revealed oligoclonal expansions consisting of Vβ5+ TCR genes that express a conserved motif composed of identical lengths, conserved joining region expression (Jβ2.5/1.4), and homologous amino acid (Ala/Gly) residues surrounding an essential Q residue. The existence of a public Vβ5+ TCR repertoire suggests selection by an identical antigen in lung, which is likely composed of HLA-DP2, peptide, and Be2+. As expected, these Vβ5+ T cells recognize the same antigen, as revealed by positive staining of CBD T cell lines with a soluble tetrameric HLA-DP2/peptide/Be2+ molecule. Interestingly, this MHCII tetramer was used to identify an additional public Vβ18+ T cell repertoire which expresses the conserved CDR3 motif found in the predominant Vβ5+ T cell population. The presence of beryllium-specific, Vβ5.1+CD4+ T cells in the lung of all DP2+ CBD patients suggests that the MHCII tetramers can be used as an early method of detection of CBD development in beryllium-exposed workers.

A rapid method to isolate and test the γ2a switched variants from a γ2b antibody producing B cell hybridoma (P3382)

The heavy chain isotype switch is reported to occur at a rate of 10-6 to 10-5 in B cell hybridomas. Because of the rare occurance, usually two or three rounds of cell sorting and subcloning are needed to isolate these variants, which is labor and time consuming. We find that the switch rate of γ2a variants in a γ2b antibody producing B cell hybridoma, S212, is around 5*10-6 by ELISPOT assay. Using the Alexa Fluor 647 conjugated goat anti-mouse IgG2a heavy chain specific antibody, we first enriched γ2a switched variants in S212 with the use of anti-AF647 microbeads. We then used the FACS to sort the single AF647 positive cell from this enriched population into a single well to ensure the single cell cloning. 18 cells were sorted into 18 wells, and there were hybridoma cells growing in 12 wells after 10 days of culture. We tested the isotype of antibody produced in the supernatant by passing it through the four channels of a CM5 chip which were respectively coated with goat anti-mouse IgG1, IgG2a, IgG2b and IgG3 heavy chain specific antibody in a Biacore instrument. The result showed that all of the 12 antibodies were IgG2a and none of them secreted IgG2b antibody any more. This method will be useful in isolating downstream Ig class switch variants of monoclonal antibodies to obtain antibodies with different Fc functions.

Host DNA released in response to aluminum adjuvant enhances MHCII mediated antigen presentation and prolongs CD4 T cell interactions with dendritic cells. (P4244)

Many vaccines include aluminum salts (alum) as adjuvants in spite of little knowledge of alum’s functions. Host DNA rapidly coats injected alum. Here we further investigated the mechanism of alum and DNA’s adjuvant function. Our data show that DNAse co-injection reduces CD4 T cell priming by intramuscularly injected antigen plus alum. This effect is partially replicated in mice lacking STING, a mediator of cellular responses to cytoplasmic DNA. Others have shown that DNAse treatment impairs alum induced DC migration from the peritoneal cavity to the draining LN. However our data shows that DNAse does not affect accumulation of, nor expression of costimulatory proteins on, antigen loaded dendritic cells in lymph nodes draining injected muscles, the site by which most human vaccines are administered. DNAse does inhibit prolonged T cell-DC conjugate formation and antigen presentation between antigen+ DCs and antigen specific CD4 T cells following intramuscular injection. Thus, from the muscle, an immunization site that does not require host DNA to promote migration of inflammatory DC, alum acts as an adjuvant by introducing host DNA into the cytoplasm of antigen-bearing DCs, where it engages receptors that promote MHC II presentation and better DC-T cell interactions.

MAIT cell recognition of MR1 bound by non-peptide antigen on bacterially infected and uninfected cells. (P5053)

Mucosal-associated invariant T cells are a unique population of T cells that express a semi-invariant αβ TCR and are restricted by the MHC class I-related molecule MR1. MAIT cells recognize uncharacterized ligand(s) presented by MR1 through the cognate interaction between their TCR and MR1. To understand how the MAIT TCR recognizes MR1 at the surface of APCs cultured both with and without bacteria, we undertook extensive mutational analysis of both the MAIT TCR and MR1 molecule. We found differential contribution of particular amino acids to the MAIT TCR-MR1 interaction based upon the presence of bacteria or bacterially-derived compounds, supporting the hypothesis that the structure of the MR1 molecules with the microbial-derived ligand(s) differs from the one with the endogenous ligand(s). Furthermore, we demonstrate that microbial-derived ligand(s) is unlikely proteinaceous or lipidaceous, arguing that a new class of antigen(s) is most likely recognized by this unique lymphocyte population.

MAIT cell recognition of MR1 on bacterially infected and uninfected cells

Mucosal-associated invariant T cells are a unique population of T cells that express a semi-invariant αβ TCR and are restricted by the MHC class I-related molecule MR1. MAIT cells recognize uncharacterized ligand(s) presented by MR1 through the cognate interaction between their TCR and MR1. To understand how the MAIT TCR recognizes MR1 at the surface of APCs cultured both with and without bacteria, we undertook extensive mutational analysis of both the MAIT TCR and MR1 molecule. We found differential contribution of particular amino acids to the MAIT TCR-MR1 interaction based upon the presence of bacteria, supporting the hypothesis that the structure of the MR1 molecules with the microbial-derived ligand(s) differs from the one with the endogenous ligand(s). Furthermore, we demonstrate that microbial-derived ligand(s) is resistant to proteinase K digestion and does not extract with common lipids, suggesting an unexpected class of antigen(s) might be recognized by this unique lymphocyte population.

Recognition of self and altered self by T cells in autoimmunity and allergy

T cell recognition of foreign peptide antigen and tolerance to self peptides is key to the proper function of the immune system. Usually, in the thymus T cells that recognize self MHC + self peptides are deleted and those with the potential to recognize self MHC + foreign peptides are selected to mature. However there are exceptions to these rules. Autoimmunity and allergy are two of the most common immune diseases that can be related to recognition of self. Many genes work together to lead to autoimmunity. Of those, particular MHC alleles are the most strongly associated, reflecting the key importance of MHC presentation of self peptides in autoimmunity. T cells specific for combinations of self MHC and self peptides may escape thymus deletion, and thus be able to drive autoimmunity, for several reasons: the relevant self peptide may be presented at low abundance in the thymus but at high level in particular peripheral tissues; the relevant self peptide may bind to MHC in an unusual register, not present in the thymus but apparent elsewhere; finally the relevant self peptide may be post translationally modified in a tissue specific fashion. In some types of allergy, the peptide + MHC combination may also be fully derived from self. However the combination in question may be modified by the presence of other ligands, such as small drug molecules or metal ions. Thus these types of allergies may act like the post translationally modified peptides involved some types of autoimmunity.

Peptide vaccines prevent tumor growth by stimulating a similar T cell repertoire as the native tumor antigen (165.46)

A major goal of immunotherapy for cancer is to focus and activate the T cell response to tumor-associated antigens. One strategy to stimulate these T cells is to immunize with specific peptides in combination immunostimulatory modalities. We are using an immunogenic mouse colon cancer model to characterize both the activating peptides and the responding T cells. We have identified peptides that interact with the restricting MHC molecule and a tumor-specific T cell clone that are either non-protective like the natural antigen, or protective against tumor challenge. The T cell repertoires responding to these peptides and the tumor are distinct, although they overlap with the natural antigen. Examination of the Vb regions expressed by the tumor-specific T cells, showed that the responses to the peptide variants were more focused than those to the natural antigen. Further ex vivo analysis showed that the T cells responding to the protective peptides and in the TIL (tumor infiltrating lymphocytes) were selected to express a CDR3b motif, which was also shared by the T cells responding to the natural antigen. We suggest that the increased signal delivered by the peptide variants that target the T cells naturally responding to the tumor such as those found in TIL result in more effective antitumor responses.

Beryllium-specific T cells adopt an unusual binding topology for antigen recognition (100.25)

Unconventional antigens, such as metals, stimulate T cells in a very specific manner. To delineate the binding landscape for metal-specific T cell recognition, alanine screens were performed on a set of beryllium (Be)-specific T cell receptors (TCR) derived from the lung of a chronic beryllium disease patient. These TCRs were HLA-DP2-restricted and expressed nearly identical Vβ5.1+ chains coupled with different Vα chains. Site-specific mutagenesis of all amino acids comprising the complementarity determining regions of TCR Vα and Vβ chains showed a dominant role for Vβ5.1 residues in Be recognition, with little contribution from the Vα domain, suggesting an abnormal binding topology. To confirm these findings, solvent-exposed residues along the α-helices of the α- and β-chains of HLA-DP2 (i.e., potential TCR contact sites) were mutated to alanine. Two β-chain residues, located near the proposed Be binding site of HLA-DP2, played a dominant role in T cell recognition, while the α-chain mutations had no effect on T cell activation. These findings strongly suggest that Be-specific T cells recognize antigen using an unconventional binding topology, with the majority of interactions contributed by residues in the TCR Vβ5.1 domain and HLA-DP2 β1-chain. We propose that unusual docking topologies are not used exclusively by T cells recognizing self-antigens, but also for the recognition of metal antigens, such as beryllium. Supported by NIH grants: HL062410 and HL092997.

Molecular targeting of islet autoantigens

Type 1 diabetes of man and animal models results from immune-mediated specific beta cell destruction. Multiple islet antigens are targets of autoimmunity and most of these are not beta cell specific. Immune responses to insulin appear to be essential for the development of diabetes of the NOD mouse. In this review, we will emphasize the unusual manner in which selected autoantigenic peptides (particularly the recently discovered target of BDC2.5 T cells [chromagranin A]) are presented and recognized by autoreactive CD4(+) T cell receptors. We hypothesize that "unusual" structural interactions of specific trimolecular complexes (MHC class II, peptide, and T cell receptors) are fundamental to the escape from the thymus of autoreactive T cells able to cause type 1 diabetes.

T cells with a specific motif in the CDR3-beta region protect mice from CT26 tumor growth (131.46)

Vaccination with peptide mimics of tumor antigens, or mimotopes, is a potential strategy for antigen-specific immunotherapy of cancer. To determine how to elicit the most effective antigen-specific cytotoxic response against tumors, we have assembled a set of mimotopes of AH1, the immunodominant antigen from the mouse CT26 tumor. Although the AH1 antigen is an ineffective immunogen, vaccination with some of the mimotopes is very successful in protecting mice from tumor growth. The majority of AH1-specific T cells responding to the vaccine or tumor express V-beta 8 gene segments. However, tumor protection by the mimotope vaccines correlates with stimulation of T cells with a more restricted TCR V-beta repertoire. These T cells express receptors that encode a relatively short CDR3-beta motif. This motif consists of a small amino acid, a non-hydrophobic amino acid, a germline-encoded tyrosine, and the J-beta 2.6 gene segment. These results suggest that protective mimotopes enhance antitumor immunity, in part, by increasing the expansion of a subset of functional tumor-specific T cells that naturally respond to the tumor, not a new repertoire of T cells only elicited by the mimotope. We will test the hypothesis that specific T cells with this motif impart increased protection because they have higher affinity for the antigen complex than specific T cells without the motif.

Sex hormone-independent capacities of female hematopoietic cells from lupus-prone mice (83.23)

Many systemic autoimmune diseases are more commonly found in females than in males. This is evident in Systemic Lupus Erythromatosis (SLE), a prototypic systemic autoimmune disorder, where the ratio of females to males is 9:1. Our current understanding of the etiology of SLE implies important roles for genes and environmental factors such as sex hormones. Analyses of mouse models of SLE have proven good models for both; however, the relative importance of genes versus sex hormones is still largely unresolved. Using the (NZB x NZW)F1 mouse model system of SLE we have created a system in which we can segregate the effects of genes and hormones on the immune system in vivo. Briefly, male or female (NZB x NZW)F1 mice were lethally irradiated and reconstituted by age-matched male or female bone marrow (BM) or fetal liver (FL) cells. The resulting chimera mice were followed for the development of lupus-like disease. We found that female BM and FL cells express an intrinsic capacity to drive accelerated lupus-like disease development even in the presence of male pubertal sex hormones. Interestingly, chimera mice receiving female cells also presented with increased serum cytokine and immunoglobulin levels, suggesting that activation of both T and B cells happened more easily in female than male cells. These data represent a new system in which to investigate intrinsic differences between male and female immune mechanisms during the development of systemic autoimmunity.

Mapping TCR recognition of a beryllium antigen with implications for chronic beryllium disease (130.17)

Exposure to the metal beryllium in the workplace can result in chronic beryllium disease (CBD), which is associated by the accumulation of large expansions of beryllium-specific CD4+ Th1 cells in the lung. Several T cell clones have been isolated from the lung of a CBD patient that recognize beryllium in the context of HLA-DPB1*0201/peptide. Sequence comparison of the TCR complementarity determining regions (CDRs) has revealed nearly identical Vβ and CDR3 Vα domains, yet different CDR1-2 Vα regions (due to expressing different TCRAV gene segments). Hence, we propose an atypical docking footprint for recognition of the beryllium antigen by these specific TCRs, with CDR1α and CDR2α not significantly contributing to T cell recognition. To test this hypothesis, we have focused on a particular Vα22+/Vβ5+ beryllium-specific TCR derived from a T cell clone designated JK28. Single-site alanine substitutions have been introduced across the CDRs of this TCR in order to delineate amino acids that are critical for recognition of the HLA-DP2/Be2+/peptide complex. TCR variants containing alanine substitutions were expressed on a murine α-β- T cell hybridoma also transduced with human CD4. Assays comparing IL-2 secretion when T cell hybridomas containing wildtype and mutated TCRs are stimulated with beryllium support the notion that the Vβ region contributes most to antigen recognition by this TCR. Supported by grants from the NIH, HL062410 and HL092997.

Nedd4 augments the adaptive immune response by promoting ubiquitin-mediated degradation of Cbl-b in activated T cells

Nedd4 and Itch are E3 ubiquitin ligases that ubiquitinate similar targets in vitro and thus are thought to function similarly. T cells lacking Itch show spontaneous activation and T helper type 2 polarization. To test whether loss of Nedd4 affects T cells in the same way, we generated Nedd4(+/+) and Nedd4(-/-) fetal liver chimeras. Nedd4(-/-) T cells developed normally but proliferated less, produced less interleukin 2 and provided inadequate help to B cells. Nedd4(-/-) T cells contained more of the E3 ubiquitin ligase Cbl-b, and Nedd4 was required for polyubiquitination of Cbl-b induced by CD28 costimulation. Our data demonstrate that Nedd4 promotes the conversion of naive T cells into activated T cells. We propose that Nedd4 and Itch ubiquitinate distinct target proteins in vivo.

Germline-encoded recognition of diverse glycolipids by natural killer T cells

Natural killer T cells expressing 'invariant' T cell receptor alpha-chains (TCRalpha chains) containing variable (V) and joining (J) region V(alpha)14-J(alpha)18 (V(alpha)14i) rearrangements recognize both endogenous and microbial glycolipids in the context of CD1d. How cells expressing an invariant TCRalpha chain and a restricted set of TCRbeta chains recognize structurally diverse antigens is not clear. Here we show that a V(alpha)14i TCR recognized many alpha-linked glycolipids by means of a 'hot-spot' of germline-encoded amino acids in complementarity-determining regions 3alpha, 1alpha and 2beta. This hot-spot did not shift during the recognition of structurally distinct antigens, suggesting that the V(alpha)14i TCR functions as a pattern-recognition receptor, conferring on natural killer T cells the ability to sense and respond in an innate way to pathogens displaying antigenic alpha-linked glycolipids.

Apoptosis and the homeostatic control of immune responses

Normal homeostasis of the immune system is controlled by a balance of production and death. During an immune response, homeostasis is disturbed as antigen-presenting cells become activated and promote the clonal expansion of antigen-specific lymphocytes. Shortly after the peak of the response, controlled induction of apoptosis, of both antigen-presenting cells and lymphocytes, restores homeostasis. This process is critical to ensure protective immunity and avoid lymphoid neoplasia and autoimmunity. Here, we will discuss recent developments in the molecular players underlying apoptotic control of immune system homeostasis.

Homeostatically proliferating CD4 T cells are involved in the pathogenesis of an Omenn syndrome murine model

Patients with Omenn syndrome (OS) have hypomorphic RAG mutations and develop varying manifestations of severe combined immunodeficiency. It is not known which symptoms are caused directly by the RAG mutations and which depend on other polymorphic genes. Our current understanding of OS is limited by the lack of an animal model. In the present study, we identified a C57BL/10 mouse with a spontaneous mutation in, and reduced activity of, RAG1. Mice bred from this animal contained high numbers of memory-phenotype T cells and experienced hepatosplenomegaly and eosinophilia, had oligoclonal T cells, and demonstrated elevated levels of IgE, major symptoms of OS. Depletion of CD4+ T cells in the mice caused a reduction in their IgE levels. Hence these "memory mutant" mice are a model for human OS; many symptoms of their disease were direct results of the Rag hypomorphism and some were caused by malfunctions of their CD4+ T cells.

Structural basis of the recognition of a methylated histone tail by JMJD2A

The Jumonji C domain is a catalytic motif that mediates histone lysine demethylation. The Jumonji C-containing oxygenase JMJD2A specifically demethylates tri- and dimethylated lysine-9 and lysine-36 of histone 3 (H3K9/36 me3/2). Here we present structures of the JMJD2A catalytic core complexed with methylated H3K36 peptide substrates in the presence of Fe(II) and N-oxalylglycine. We found that the interaction between JMJD2A and peptides largely involves the main chains of the enzyme and the peptide. The peptide-binding specificity is primarily determined by the primary structure of the peptide, which explains the specificity of JMJD2A for methylated H3K9 and H3K36 instead of other methylated residues such as H3K27. The specificity for a particular methyl group, however, is affected by multiple factors, such as space and the electrostatic environment in the catalytic center of the enzyme. These results provide insights into the mechanisms and specificity of histone demethylation.

Ndfip1 protein promotes the function of itch ubiquitin ligase to prevent T cell activation and T helper 2 cell-mediated inflammation

Nedd4 family interacting protein-1 (Ndfip1) is a protein whose only known function is that it binds Nedd4, a HECT-type E3 ubiquitin ligase. Here we show that mice lacking Ndfip1 developed severe inflammation of the skin and lung and died prematurely. This condition was due to a defect in Ndfip1(-/-) T cells. Ndfip1(-/-) T cells were activated, and they proliferated and adopted a T helper 2 (Th2) phenotype more readily than did their Ndfip1(+/+) counterparts. This phenotype resembled that of Itchy mutant mice, suggesting that Ndfip1 might affect the function of Itch, an E3 ubiquitin ligase. We show that T cell activation promoted both Ndfip1 expression and its association with Itch. In the absence of Ndfip1, JunB half-life was prolonged after T cell activation. Thus, in the absence of Ndfip1, Itch is inactive and JunB accumulates. As a result, T cells produce Th2 cytokines and promote Th2-mediated inflammatory disease.

Genetic susceptibility to polyI:C-induced IFNalpha/beta-dependent accelerated disease in lupus-prone mice

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown etiology. Associations between viral infections and the onset of SLE have been suggested, and recent studies have provided evidence that type I interferons (IFNalpha/beta) might play a role in the SLE disease process. Viruses and interferons have also been implicated in mouse models of SLE. We generated a model of accelerated proteinuria, in which lupus-prone mice were injected repeatedly with polyinosinic:polycytidylic acid (polyI:C), mimicking exposure to virus-derived double stranded RNA (dsRNA), leading to the production of IFNalpha/beta. PolyI:C-treated (B6.Nba2 x NZW)F1 and (B6 x NZW)F1 hybrid mice developed significantly increased levels of anti-dsDNA autoantibodies, characteristic of lupus. Most significantly, polyI:C-treated (B6.Nba2 x NZW)F1 mice, but not (B6 x NZW)F1 or parental strains, developed lupus-like nephritis in an accelerated fashion, which was dependent on IFNalpha/beta and associated with elevated deposition of total IgG, IgG2a and complement factor C3 in the glomerular capillary walls. These data suggest that reagents, which increase the levels of endogenous IFNalpha/beta (directly or indirectly), can accelerate the course of lupus-like nephritis, the development of which is dependent on the presence of both NZW- and Nba2-encoded genes.

Bax does not have to adopt its final form to drive T cell death

The introduction of antigen into animals causes antigen-specific T cells to divide and then die. Activated T cell death requires either of the death effector molecules, Bak or Bax. When T cells die, Bak and Bax change their conformations, a phenomenon that is thought to be required for Bak or Bax to drive cell death. Here we show that Bak changes conformation before activated T cells die, as detected by an antibody specific for a peptide near the NH2 terminus of Bak, but Bax does not change its shape markedly until after the cells are dead, as detected by an antibody specific for a peptide near the NH2 terminus of Bax. This latter finding is also true in activated T cells that lack Bak and are therefore dependent on Bax to die. This result suggests that Bax does not have to adopt its final, completely unfolded form until after the cells are dead.

Loss of the proapoptotic protein, Bim, breaks B cell anergy

Although B cells that respond with high avidity to self-antigen are eliminated early in their development, many autoreactive B cells escape elimination and are tolerized later in their lives via anergy. Anergic B cells are unresponsive to antigen and die prematurely. It has been suggested that the proapoptotic protein, Bim, controls the fate of anergic B cells. To test this idea, mice lacking Bim were crossed with mice that express soluble hen egg lysozyme and whose B cells bear receptors specific for the protein. In Bim^+/+ mice these B cells are anergic and die rapidly. If the mice lack Bim, however, the B cells live longer, are more mature, respond to antigen, and secrete anti–hen egg lysozyme antibodies. This break of tolerance is not due to expression of endogenous B cell receptors, nor is it dependent on T cells. Rather, it appears to be due to a reduced requirement for the cytokine BAFF. Normal B cells require BAFF both for differentiation and survival. Bim^−/− B cells, on the other hand, require BAFF only for differentiation. Therefore, autoreactive B cells are allowed to survive if they lack Bim and thus accumulate sufficient signals from differentiating factors to drive their maturation and production of autoantibodies.

Class II major histocompatibility complex-peptide tetramer staining in relation to functional avidity and T cell receptor diversity in the mouse CD4(+) T cell response to a rheumatoid arthritis-associated antigen

OBJECTIVE

Although studies have suggested that human cartilage (HC) gp-39 may be an antigen recognized by autoreactive CD4(+) T cells in rheumatoid arthritis, we previously failed to identify specific CD4(+) T cells in patients' synovial fluid or blood using a class II major histocompatibility complex-peptide tetramer composed of the immunodominant HC gp-39(263-275) epitope covalently linked to DR4. We undertook this study to better understand the parameters for specific binding of this tetramer.

METHODS

DR4-transgenic mice were immunized with the HC gp-39 peptide, and a set of peptide-responsive hybridomas was derived. Hybridomas were stained with the DR4-gp-39 tetramer and cultured with increasing amounts of peptide in the presence of DR4-expressing antigen-presenting cells to determine functional avidity.

RESULTS

Great variability was apparent in the ability of the tetramer to stain the hybridomas, and there was a strong correlation between the intensity of tetramer staining and functional avidity. Importantly, nearly 30% of the hybridomas did not stain with tetramer, and these cells exhibited relatively low functional avidity. Although the addition of an anti-T cell receptor (anti-TCR) monoclonal antibody during the staining procedure enhanced binding of the tetramer to a number of the hybridomas, a significant percentage remained unstainable. Analysis of TCR expression showed that >90% of the hybridomas expressed the same TCR beta-chain variable region (V(beta)10), and sequencing of the TCR junctional regions showed diversity in the third complementarity-determining region.

CONCLUSION

These results suggest that immune responses dominated by relatively low-affinity TCR interactions, such as those that may occur in autoimmune disease, will be difficult to detect using standard tetramer techniques.

Loss of Bim allows precursor B cell survival but not precursor B cell differentiation in the absence of interleukin 7

Interleukin (IL)-7 is a stromal cell-derived cytokine required for the survival, proliferation, and differentiation of B cell precursors. Members of the Bcl-2 family of proteins are known to have profound effects on lymphocyte survival, but not lymphocyte differentiation. To distinguish the relative dependence on IL-7 of B cell precursor survival versus B cell differentiation, the combined effects of lack of IL-7 and lack of the proapoptotic Bcl-2 relative, Bim, were studied. Bim is expressed to varying degrees in all B cell precursors and B cells. Lack of Bim compensated for lack of IL-7 in the survival of pro-, pre-, and immature B cells; however, lack of Bim did not substitute for the requirement for IL-7 in B cell precursor differentiation or B cell precursor proliferation. Precursor B cell survival is more dependent on sufficient levels of IL-7 than precursor B cell differentiation because the number of B cells and their precursors were reduced by half in mice heterozygous for IL-7 expression, but were restored to normal numbers in mice also lacking Bim. Hence, Bim and IL-7 work together to control the survival of B cell precursors and the number of B cells that exist in animals.

Control of T cell viability

The factors affecting T cell viability vary depending on the type and status of the T cell involved. Naive T cells die via a Bcl-2/Bim dependent route. Their deaths are prevented in animals by IL-7 and contact with MHC. Activated T cells die in many different ways. Among these is a pathway involving signals that come from outside the T cell and affect it via surface receptors such as Fas. Activated T cells also die through a pathway driven by signals generated within the T cell itself, a cell autonomous route. This pathway involves members of the Bcl-2 family, in particular Bcl-2, Bcl-xl, Bim, and probably Bak. The viability of CD8+ and CD4+ memory T cells is controlled in different ways. CD8+ memory T cells are maintained by IL-15 and IL-7. The control of CD4+ memory T cells is more mysterious, with roles reported for IL-7 and/or contact via the TCR.

Promotion of B cell immune responses via an alum-induced myeloid cell population

Exposure of naïve B cells to the cytokine interleukin-4 (IL-4) and/or antigen leads to a state of "priming," in which subsequent aggregation of major histocompatibility complex class II molecules induces the mobilization of calcium ions and cell proliferation. However, it is not clear how critical this priming is for immune responses or how it is normally induced in vivo. Injection of mice with the commonly used adjuvant alum led to priming of splenic B cells and to the accumulation in the spleen of a previously unknown population of IL-4-producing, Gr1+ cells. These cells and IL-4 were both required for in vivo priming and expansion of antigen-specific B cells, as well as for optimal production of antibody. These studies reveal a key role for a previously unknown accessory myeloid cell population in the generation of humoral immune responses.

Constitutive association of the proapoptotic protein Bim with Bcl-2-related proteins on mitochondria in T cells

Apoptosis in activated T cells in vivo requires the proapoptotic Bcl-2 family member Bim. We show here that, despite its ability to bind LC8, a component of the microtubule dynein motor complex, most of the Bim in both healthy and apoptotic T cells is associated with mitochondria, not microtubules. In healthy resting T cells Bim is bound to the antiapoptotic proteins Bcl-2 and Bcl-x(L). In activated T cells, levels of Bcl-2 fall, and Bim is associated more with Bcl-x(L) and less with Bcl-2. Our results indicate that, in T cells, Bim function is regulated by interaction with Bcl-2 family members on mitochondria rather than by sequestration to the microtubules.

Commentary: TCR–MHC/peptide interactions: kissing-cousins or a shotgun wedding?

The purpose of this Commentary is to put into modern-day perspective Jerne's hypothesis that antigen receptors encoded in the genome have been evolutionarily selected for their ability to react with major histocompatibility proteins and that the process of eliminating self reactivity is the catalyst for the generation of diversity of antigen receptors. In writing his hypothesis Jerne was trying to deal with the obsession of the immune system with the MHC, an obsession that was manifest in his days by the strong reactions of the immune system with allogeneic MHC proteins. However, Jerne's hypothesis also took on other issues that were not understood at the time--issues that included lymphocyte selection and tolerance, the generation of somatic diversity and the ability of the MHC to control responses to other antigens. In so doing, Jerne generated a hypothesis that accounted remarkably satisfactorily for what was known in 1971. Whilst the details of much of the hypothesis have since turned out to be incorrect, in his ideas Jerne did anticipate many of the most interesting and surprising findings of the subsequent 33 years.