Analysis of major histocompatibility complex class I-restricted hapten recognition by mutation of the V-J joining of T cell receptor alpha chains.

Hapten-specific T cell responses are responsible for chemically induced immune disorders. However, the molecular details of hapten interactions with T cell receptors (TCR) are poorly understood. Recent studies of trinitrophenyl (TNP)-specific responses revealed major histocompatibility complex-associated TNP-peptides as dominant epitopes for CD8+ and CD4+ T cells. The present study is based on the observation that two H-2Kb/TNP-specific CTL clones (II/7 and III/1), differing exclusively in two amino acids of their TCR alpha chains, also differed in their carrier specificities for various TNP-peptides. The genes of the two alpha chains and the common beta chain were cloned into expression vectors. Transfection of the TCR alpha chain of clone III/1 into a hybridoma of clone II/7 also transferred the fine specificity of clone III/1, indicating that the small alpha chain variations were indeed responsible for the different carrier specificities. Point mutations bridging the difference between the alpha chains of clones II/7 and III/1 and functional studies of the respective TCR alpha beta transfectants into a TCR-negative hybridoma revealed an unexpected result: the two receptors did not represent examples of structural complementarity for different sets of hapten-peptide conjugates; rather, they resembled two structures of principally similar specificity but of significantly different overall affinity. This was demonstrated more directly by comparing the fine specificities of III/1 transfectants expressing or not expressing the co-receptor CD8: the CD8-negative III/1 transfectant assumed a specificity pattern indistinguishable from that of a CD8-expressing, II/7-derived transfectant. Hence, comparable alterations of antigen recognition may be induced either by subtle TCR alterations or by removal of CD8, i.e. by the presence or absence of a non-polymorphic adhesion molecule.

Carrier-reactive hapten-specific cytotoxic T lymphocyte clones originate from a highly preselected T cell repertoire: implications for chemical-induced self-reactivity.

We have recently described trinitrophenyl (TNP)-specific cytotoxic T lymphocyte (CTL) clones from C57BL/6 mice specific for hapten-modified peptides bearing a TNP-lysine in a peripheral position, i.e. in position 7 of H-2Kb-bound octapeptides. CTL recognition of such determinants is always sequence-dependent due to co-recognition of TNP as well as amino acid side chains of the carrier peptide. By the use of glycine-based designer peptides for primary induction of CTL in vitro, we have identified two sub-epitopes on individual position 7-haptenated peptides that form two TcR contact points and which can be independently recognized by cloned CTL. One of these sub-epitopes is represented by the hapten itself, the other by the amino acids tyrosine and lysine in positions 3 and 4 of the carrier peptide, respectively. Immunization with such TNP-modified peptides frequently results in the specific induction of CTL also reacting with the unmodified carrier peptides. DNA sequence analyses of the TcR revealed an extraordinary similarity of several independent TcR of CTL from individual mice and induced with different TNP-peptides. These receptor similarities clearly correlate with structural elements common to the immunizing peptides and suggest their origin from positive thymic selection of TcR on Kb-associated associated self-peptides bearing Tyr in position 3. Our data provide additional information concerning the topology of TcR binding to peptide/MHC complexes with, but also without, TNP. They also indicate a mechanism which might explain the potential of chemicals or drugs to induce autoimmune phenomena.

Cross-reactive trinitrophenylated peptides as antigens for class II major histocompatibility complex-restricted T cells and inducers of contact sensitivity in mice. Limited T cell receptor repertoire.

The induction of contact sensitivity in mice by hapten reagents such as trinitrochlorobenzene (TNCB) involves the activation of class II major histocompatibility complex (MHC)-restricted, hapten-specific, CD4+ T cells. Reports from different laboratories have indicated that the relevant antigenic epitopes in such reactions might include hapten-conjugated, MHC class II-associated peptides. This study for the first time directly demonstrates that hapten-peptides account for the majority of determinants recognized by trinitrophenyl (TNP)-specific CD4+ T lymphocytes. The sequences of those TNP carrier peptides do not have to be related to mouse proteins. Thus, we show that TNP-modified peptides derived from mouse IgG, pigeon cytochrome c or staphylococcal nuclease known to bind to I-Ab or from lambda repressor with specificity to I-Ad as well as TNP-proteins such as bovine serum albumin, ovalbumin or keyhole limpet hemocyanin all create class II-restricted hapten determinants for a number of TNP-specific T cell clones and hybridomas. All of these cells were induced with cells modified by trinitrobenzene sulfonic acid (TNBS). In addition, we present arguments indicating that individual TNP-specific helper T cells may cross-react with different TNP-peptides bound to identical class II molecules. Chemical treatment of antigen-presenting cells with TNCB or TNBS may thus result in a limited number of particularly repetitive immunodominant hapten epitopes. Immunodominant epitopes were also indicated by an overrepresentation of the TCR elements V beta 2 and V alpha 10 in I-Ab/TNP-specific T cells. Most importantly, however, we demonstrate that TNP attached to lysine 97 in the staphylococcal nuclease peptide 93-105 (i.e. a clearly "non-self" sequence) is able to prime mice for subsequent elicitation of contact sensitivity by TNCB in the absence of foreign protein. We take this to indicate that those TNP-peptide determinants defined by us as immuno-dominant are responsible for the induction of contact sensitivity to haptens.

Antigen contact sites in class I major histocompatibility complex-restricted, trinitrophenyl-specific T cell receptors.

Cloned trinitrophenyl (TNP)-specific cytotoxic T cells (CTL) were obtained from mice transgenic for the beta chain of the antigen-specific receptor (TcR) of a Kb-restricted, TNP-specific CTL clone (BT7.4.1). The transgene-expressing CTL, specific for TNP/Kb were found to select for TcR alpha chains highly similar to that of the transgene donor clone BT7.4.1. In that way, two clones (II/7 and III/1) were identified whose TcR differed from the BT7.4.1 receptor only in their N alpha- and J alpha-sequences, i.e. within the third complementarity-determining regions of their alpha chains (CDR3 alpha). Moreover, the TcR of clones II/7 and III/1 had both rearranged the same J alpha element, thus differing from each other by only two amino acids in their V alpha/J alpha junctional regions. Functionally, however, clone III/1 exhibited unique cytolytic specificities for synthetic, Kb-binding TNP-peptides as well as for chemically TNP-modified allogeneic (H-2k) target cells. These findings demonstrate that (a) similar to "conventional" peptide antigens, synthetic hapten-peptide determinants are contacted by CDR3 alpha-determined amino acids of the TcR and (b) in contrast to current models, CDR alpha also appears to influence the major histocompatibility complex restriction specificity of a given TcR.

Time course of wound healing.

Wound healing is a special kind of inflammation. Undisturbed wound healing is subject to a fixed time schedule of biochemical and cellular events. It is virtually impossible to deal with the time course of wound healing without describing the cellular and non-cellular events involved. The activity and mode of cell action after injury are coordinated by spatial and chronological factors, as well as by different mediators and cell-cell interacting signals. During wound healing the sequence of different signals and message substances, such as mediators of inflammation, fulfill a key function in wound repair. The report describes the time course of healing and the control of cellular events by different mediators and cell interactions. Emphasis is placed on temporal aspects, including the various signals leading to typical cellular events in wound healing.

[Animal rights--new questions about animal ethics]. / Tierrechte--neue Fragen zur Tierethik.

The assertion that animals have interests and rights comparable to those of humans raises some new questions: How should unavoidable conflicts between man and animal be solved? How should a decision be taken in a conflict between human demands of no vital necessity e.g. the consumption of meat or mobility, and the right of animals to live? The answers to these questions illustrate the scope and limitations of ethical discussions. In spite of this solutions have to be elaborated based on conscience, ideas of a fair partnership and theological considerations.

Chemical and physical properties of a hydrogel wound dressing.

Geliperm hydrogel provides optimal physiological conditions for wound healing. The material is composed of two interlaced networks, one of polyacrylamide and one of agar, and contains about 96% firmly bound water. It is supplied in smooth, elastic, transparent sheets which are impermeable to bacteria but permeable to gases, salts, metabolites and proteins. Geliperm is nontoxic and has no irritative properties. Mechanical properties, water retention and diffusion of dyes and proteins are reported. Bacterial size should preclude penetration of the gel. The hydrogel in granular form represents a coherent material which could be used in deep fissured wounds and for the treatment of injuries with a large amount of exudation and contamination.

[Continuous monitoring of blood gases in adults]. / Die kontinuierliche Uberwaschung der Blutgase beim Erwachsenen.

Single blood gas analysis offers only a momentary value, whereas with continuous monitoring of blood gases their development can be followed very closely. Cutaneous pO2 monitoring has not proved successful in adults, since the measured values depend very much on the condition of the skin, local perfusion, and cardiac output. On the other hand, continuous intravascular pO2 monitoring does represent a relatively safe and convenient method of supervision. At this institute a cutaneous pCO2-sensor developed by the Bio-Electronics Department of F. Hoffmann-La Roche & Co. Ltd. with sensor temperatures of 41 degrees, 43 degrees, and 44 degrees C has been tested. The coefficients of correlation are 0.95 or even higher for all three sensor temperatures. At a sensor temperature of 41 degrees C the reaction velocity is markedly reduced. Accuracy and reaction velocity for the sensor temperatures of 43 degrees and 44 degrees C are equivalent, but at a temperature of 43 degrees C there are fewer and slighter skin reactions. The authors found a slight drift of 0.2--0.3 mm Hg/h. The dependence of cutaneous pCO2 on local perfusion and cardiac output also appears to be slight.