The carrier effect in the secondary response to hapten-protein conjugates. 3. The anatomical distribution of helper cells and antibody-forming-cell-precursors

DCs at the center of help: Origins and evolution of the three-cell-type hypothesis

Last year was the 10th anniversary of Ralph Steinman's Nobel Prize awarded for his discovery of dendritic cells (DCs), while next year brings the 50th anniversary of that discovery. Current models of anti-viral and anti-tumor immunity rest solidly on Steinman's discovery of DCs, but also rely on two seemingly unrelated phenomena, also reported in the mid-1970s: the discoveries of "help" for cytolytic T cell responses by Cantor and Boyse in 1974 and "cross-priming" by Bevan in 1976. Decades of subsequent work, controversy, and conceptual changes have gradually merged these three discoveries into current models of cell-mediated immunity against viruses and tumors.

High-affinity anti-glycan antibodies: challenges and strategies

High-affinity binding of antibodies provides for increased specificity and usually higher effector functions in vivo. This goal, well documented in cancer immunotherapy, is very relevant to vaccines as well, and has particularly significant application toward glycan antigens. The inability to elicit high-affinity antibodies has limited potential applications of glycan-based immunogens, giving rise to insufficient population coverage due to low titers and short duration of protection. That such vaccines have achieved widespread use in spite of these shortcomings highlights the surpassing importance of glycans as prophylactic immunological targets. New advances in the combination of synthetic chemistry, bioconjugation, and mechanistic immunology offer the possibility to vastly expand the number of potential molecular targets in cancer and infectious diseases by opening a wider world of carbohydrate structures to immunological recognition and high-affinity response.

Medawar's legacy to cellular immunology and clinical transplantation: a commentary on Billingham, Brent and Medawar (1956) 'Quantitative studies on tissue transplantation immunity. III. Actively acquired tolerance'

‘Quantitative studies on tissue transplantation immunity. III. Actively acquired tolerance’, published in Philosophical Transactions B in 1956 by Peter Medawar and his colleagues, PhD graduate Leslie Brent and postdoctoral fellow Rupert Billingham, is a full description of the concept of acquired transplantation tolerance. Their 1953 Nature paper (Billingham RE et al. 1953 Nature172, 603–606. (doi:10.1038/172603a0)) had provided initial evidence with experimental results from a small number of neonatal mice, with mention of similar findings in chicks. The Philosophical Transactions B 1956 paper is clothed with an astonishing amount of further experimental detail. It is written in Peter Medawar's landmark style: witty, perceptive and full of images that can be recalled even when details of the supporting information have faded. Those images are provided not just by a series of 20 colour plates showing skin graft recipient mice, rats, rabbits, chickens and duck, bearing fur or plumage of donor origin, but by his choice of metaphor, simile and analogy to express the questions being addressed and the interpretation of their results, along with those of relevant published data and his prescient ideas of what the results might portend. This work influenced both immunology researchers and clinicians and helped to lay the foundations for successful transplantation programmes. It led to the award of a Nobel prize in 1960 to Medawar, and subsequently to several scientists who advanced these areas. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

Activation rules: the two-signal theories of immune activation

Two-signal theories of lymphocyte activation have evolved considerably over the past 35 years. In this article, we examine the contemporary experimental observations and theoretical concerns that have helped to forge the most influential variants of the theory. We also propose that more-rigorous quantitative methods are required to sustain theoretical development in the future.

The effect of specific cell inactivation on the cellular immune response to ferredoxin peptides

Previous studies using synthetic immunogenic molecules containing two haptenic peptides (ther NH2-terminal heptapeptide and the COOH-terminal pentapeptide of oxidized ferredoxin (O-Fd) from C. pasteurianum) have shown that both peptides individually are capable of initiating lymphocyte transformation and inhibiting migration in populations of lymphocytes from O-Fd-sensitized guinea pigs. While migration inhibition could readily be stimulated by single haptenic peptides, lymphocyte treasformation appeared to be more easily induced by molecules containing two or more haptenic peptides (these could be identical or different) (Kelly, B., Levy, J.G. and Hull, D., Eur. J. Immunol., 1973. 3:574). If lymphocyte transformation is a T cell-mediated phenomenon, these observations indicate the possibility of T cell-T cell interaction. The two haptenic peptides (designated "N" and "C") were synthesized and conjugated to succinylated bovine serum albumin (S-BSA), forming the conjugates N-S-BSA and C-S-BSA, respectively. These conjugates were labeled to high specific activity with 125iodine and were used in an "antigen suicide" procedure to treat guinea pig lymph node cell preparations previously sensitized to O-Fd and keyhole limpet hemocyanin (KLH). Cell populations exposed to either 125I-labeled C-S-BCA demonstrated decreased lymphocyte transformation in the presence of O-Fd but not in the presence of KLH. These results indicate specific cell inactivation by the radioactive peptide conjugates of those cells responsible for initiating cell transformation. Experiments performed by mixing 125I-labeled N-S-BSA-treated cells with 125I-labeled C-S-BSA-treated cells were successful in partially restoring the response to O-Fd and suggest possible synergy between N and C determinant binding cells in the cellular immune response to O-Fd. Evidence from B cell depletion studies suggests that this is a T cell-T cell interaction.

Lack of a correlation between cell-mediated immunity to the carrier and the carrier-hapten helper effect

The relationship between cell-mediated immunity to the carrier and the carrier-hapten helper effect was studied in the rat by using three forms of the carrier which differed in their capacity to induce carrier-specific delayed-type hypersensitivity. The three carriers were polymerized flagellin (POL), flagellin (FIN), and acetoacetylated flagellin (AFIN), which induced FIN-specific delayed-type hypersensitivity in the order AFIN > FIN > POL. Helper cells for the anti-DNP antibody responses to a range of DNP-FIN conjugates appeared to be almost inversely related to cell-mediated immunity to the carrier, being in the order POL > FIN =/> AFIN. These differences occurred whether the carriers were injected in saline or FCA, but were less pronounced with the heavily DNP-conjugated flagellins.

Synergy among lymphoid cells mediating the graft-versus-host response. 3. Evidence for interaction between two types of thymus-derived cells

Two types of thymus-derived (T) lymphocytes have been shown to cooperate in the induction of graft-versus-host responses. One cell type is found in highest concentrations in the peripheral blood and lymph node, is extremely sensitive to anti-thymocyte serum (ATS) in vivo, and is probably part of the recirculating lymphoid cell pool (3). The second cell type, found in highest concentrations in the thymus and spleen, is relatively resistant to small doses of ATS in vivo. Both cell types are substantially depleted after neonatal thymectomy. Moreover, since synergism was also obtained using appropriate mixtures of cells from either parental strain in F(1) hosts, it was possible to show that the nonrecirculating cells determined the specificity of the response and were probably the precursors of effector cells in this response. The recirculating T cell appeared to amplify this response. The implications of these data are discussed.