[Revision prosthesis for the hip joint in severe bone loss]

When total hip prostheses loosen after initial implantation and subsequent prosthesis replacement, increasing bone resorption occurs in the bed of the prosthesis. Finally, a very thin cortex remains in the bed of the prosthesis, which no longer provides sufficient mechanical stability. The replacement prosthesis described, which is anchored in the distal medullary canal without cement, provides a bridge over the damaged prosthesis bed and results in a condition of relative mechanical stability. After implantation of the replacement prosthesis, lively proliferation of the bone tissue occurs in the old prosthesis bed, which again replaces the bone loss that had taken place previously. The late results that would permit a final assessment of the procedure are not yet available.

Frequency analysis of class I MHC-reactive Lyt-2+ and class II MHC-reactive L3T4+ IL 2-secreting T lymphocytes

The reactivity of Lyt-2+ or L3T4+ T cells stimulated with either mutant class I or class II MHC alloantigens was studied. Whereas stimulation with class I MHC antigens induced only Lyt-2+ T cells to proliferate and to secrete IL 2, stimulation with class II MHC alloantigens induced L3T4+ but not Lyt-2+ T cells. When the frequencies of precursors of IL 2-secreting T lymphocytes (IL 2TL-p) were determined by limiting dilution analyses, class I MHC-reactive Lyt-2+ T cells displayed frequencies (f = 1/200) as high in magnitude as those within class II MHC-reactive L3T4+ (f = 1/100). Clonally developing IL 2TL of either T cell subset were antigen-specific, as shown in split-culture experiments. Whereas L3T4+ helper TL could be induced to specific IL 2 secretion over a long time period (days 3 to 9), Lyt-2+ TL showed a marked time optimal on day 4; thereafter, the number of TL colonies inducible to secrete IL 2 decreased steadily. IL 2 production and IL 2TL-p frequencies of unseparated T responder cells were not the numerical superposition of the two individual T cell subsets (Lyt-2+ + L3T4+); the latter finding is likely to reflect regulatory influences of Lyt-2+ T cells on IL 2-secreting L3T4+ T cells.

Frequency analysis of class I MHC-reactive Lyt-2+ and class II MHC-reactive L3T4+ IL 2-secreting T lymphocytes

The reactivity of Lyt-2+ or L3T4+ T cells stimulated with either mutant class I or class II MHC alloantigens was studied. Whereas stimulation with class I MHC antigens induced only Lyt-2+ T cells to proliferate and to secrete IL 2, stimulation with class II MHC alloantigens induced L3T4+ but not Lyt-2+ T cells. When the frequencies of precursors of IL 2-secreting T lymphocytes (IL 2TL-p) were determined by limiting dilution analyses, class I MHC-reactive Lyt-2+ T cells displayed frequencies (f = 1/200) as high in magnitude as those within class II MHC-reactive L3T4+ (f = 1/100). Clonally developing IL 2TL of either T cell subset were antigen-specific, as shown in split-culture experiments. Whereas L3T4+ helper TL could be induced to specific IL 2 secretion over a long time period (days 3 to 9), Lyt-2+ TL showed a marked time optimal on day 4; thereafter, the number of TL colonies inducible to secrete IL 2 decreased steadily. IL 2 production and IL 2TL-p frequencies of unseparated T responder cells were not the numerical superposition of the two individual T cell subsets (Lyt-2+ + L3T4+); the latter finding is likely to reflect regulatory influences of Lyt-2+ T cells on IL 2-secreting L3T4+ T cells.

The Berlin cochlear implant--surgical concept

The extent of channel interactions using monopolar extrascalar stimulation probably limits the number of independently acting electrodes of a cochlear implant to three. Comparison of psychoacoustic and histopathological findings led to the conclusion that stimulation of the neurons in the upper basal and the second coil is of greatest benefit to the patient. By using a middle fossa approach, access to the upper basal coil and the second coil is possible without destruction of middle ear structures. The danger of infection is probably reduced. Using an additional external round-window electrode, a device providing three different stimulating electrodes can be applied.

Human cytotoxic T lymphocytes. II. Frequency analysis of cyclosporin A-sensitive alloreactive cytotoxic T-lymphocyte precursors

A limiting dilution (LD) culture system was used to investigate the effect of cyclosporin A (CsA) on the activation and differentiation of human alloreactive cytotoxic T-lymphocyte precursors (CTL-p). CsA reduced in a dose-dependent fashion the frequency of alloantigen-inducible CTL-p. With most normal individuals tested there was a 20- to 50-fold reduction of alloreactive CTL-p frequencies in the presence of 500-1000 ng/ml CsA. Both unseparated T cells and CD8+ T cells were CsA-sensitive under LD culture conditions. Importantly, however, alloreactive CTL-p from two out of 21 normal individuals were found to be largely CsA-resistant. CsA did not affect the growth of MLR-primed CTL in secondary LD culture. Furthermore, CsA slightly inhibited the cytolytic activity of some alloantigen-specific CTL clones. These results are discussed with respect to the clinical use of CsA in transplantation medicine.

Selective reduction of donor-specific cytotoxic T lymphocyte precursors in patients with a well-functioning kidney allograft

We have recently developed a sensitive limiting dilution (LD) culture system to measure human alloreactive cytotoxic T lymphocyte precursors (CTL-p) in a given lymphoid cell population. We have now used this system to determine frequencies of donor HLA antigen-inducible CTL-p in the peripheral blood of human allograft recipients at various stages after transplantation. All patients (1 pancreas recipient and 9 kidney recipients) were on continuous cyclosporine treatment throughout the study. We report that, in patients with a well-functioning kidney graft (6/9), the number of donor-reactive CTL-p among peripheral blood lymphocytes decreased within 3-8 months after transplantation--in some cases (2/6) more than 10-fold. In contrast, frequencies of CTL-p with specificity for third-part HLA antigens remained largely unaltered in these patients. Furthermore, no decrease of donor-reactive CTL-p frequencies was seen in 3 of 4 patients showing clinical symptoms of graft rejection. These results indicate that functional clonal deletion of antigraft-reactive CTL-p may contribute to the state of graft tolerance in certain patients with a well-functioning kidney allograft.

Identification of interleukin 2-producing T helper cells within murine Lyt-2+ T lymphocytes: frequency, specificity and clonal segregation from Lyt-2+ precursors of cytotoxic T lymphocytes

The prime aim of this study was to assess whether the autonomous primary mixed lymphocyte culture response of Lyt-2+ T cells towards class I major histocompatibility complex (MHC) antigens reflects in terms of interleukin 2 (IL2) production and cytotoxicity the activation of multifunctional Lyt-2+ T cells, or the activation of functionally distinct T cell subsets. The results demonstrate that highly purified Lyt-2+ T cells proliferate in response to class I MHC antigens, as opposed to L3T4+ T cells which react towards class II MHC antigens. In both responder cell types proliferative responses are associated with IL2 secretion, while only Lyt-2+ T cells develop measurable cytotoxic effector cells. The precursor frequency of IL2-producing helper cells in MHC class I-reactive Lyt-2+ T cells equals that in MHC class II-reactive L3T4+ T cells (f = 1/500-1/1000). In clonal segregation analysis greater than 90% of Lyt-2+ colonies secreting IL2 do not develop cytotoxic activity, while greater than 90% of Lyt-2+ cytotoxic T cells fail to produce detectable IL2. A minority of less than 10% of Lyt-2+ T cells appears to be bifunctional. As such the results point out the existence of functionally committed T cells within class I MHC-reactive Lyt-2+ T cells able to produce either IL2 or to develop into cytotoxic effector cells.

Human mumps virus-specific cytotoxic T lymphocytes: quantitative analysis of HLA restriction

To obtain quantitative information about the use of HLA antigens as restriction element by antiviral cytotoxic T lymphocytes (CTL), we have analyzed precursors of human mumps virus-specific CTL by limiting dilution. CTL generated by restimulation of peripheral blood T lymphocytes with autologous mumps virus (MV)-infected stimulator cells were restricted by autologous HLA class I antigens, and derived from the T4-8+ population. They were specific for MV and did not lyse autologous target cells infected with other viruses. Frequencies of MV-specific CTL precursors ranged from 1/500 to 1/8000. HLA restriction was analyzed by split-well analysis of individual CTL colonies. CTL recognizing HLA-A or B antigens were unequally distributed: HLA-B7, -B13, and -B27 were found to function as predominant, in some cases as exclusive, restriction elements, whereas other antigens such as HLA-A24 were never or rarely used. In several combinations, there was no evidence for antigenic variants of HLA molecules as reason for the failure to be recognized. The proportion of CTL precursors recognizing HLA-A2 and -B8 seemed to be dependent on the presence or absence of "dominant" restriction elements. We conclude that CTL precursors recognizing certain virus-HLA combinations are preferentially expanded during an infection, but that low responsiveness to a given combination is not necessarily absolute.

Functional and biochemical characteristics of a murine interleukin 2 receptor-inducing factor

High density (resting) murine Lyt-2+ T cells exposed in vitro to the ligand concanavalin A (Con A) remain interleukin 2 (IL 2) unresponsive, i.e. do not express functional IL 2 receptors, unless reconstituted with accessory cells. This finding provides a bio-assay to define functional and biochemical characteristics of an IL 2 receptor-inducing factor (RIF). RIF bioactivity as secreted from the macrophage cell line P388-D1 is associated with a trypsin-sensitive protein of 44 kDa which does not need to be glycosylated and which binds to and can be eluted from hydroxylapatite and phenyl-Sepharose. While both RIF and IL 1 are produced by accessory cells the lymphokines separate from each other according to functional and biochemical criteria. Either accessory cells, RIF or the protein kinase C activator phorbol myristate acetate can substitute for each other and are equally active for the induction of IL 2 responsiveness in high-density Lyt-2+ T cells exposed to Con A. To explain these results we conclude that in the mitogen system used, induction of IL 2 responsiveness (activation) represents a two-step event in which first cross-linking of cell surface structures by the ligand Con A excites the responder T cells, which subsequently respond to the accessory cell product RIF.

Clonal activation of cytotoxic lymphocyte precursors by monoclonal anti-CD3 antibody: analysis of feeder cell requirements

Activation of cytotoxic lymphocyte precursors (CLP) by the mitogenic monoclonal anti-CD3 antibody OKT3 was studied under limiting dilution (LD) culture conditions. One out of 2-6 E-rosette-purified T cells gave rise to a cytotoxic T cell (CTL) clone when cultured in the presence of OKT3 (0.2-2 ng/ml), recombinant IL-2 (100 U/ml), and irradiated feeder cells. Clonal CLP activation was optimally supported by a combination of E-rosette-depleted non-T feeder cells with small numbers of T cells added back. Among the cell lines tested, Fc-receptor-bearing monocytic cell lines U937 and HL-60 were efficient feeder cells whereas T cell lines (Jurkat, Molt-4, Ke37) did not support clonal CLP activation. These data indicate that clonal activation of CLP and differentiation into cytotoxic effector cells under LD culture conditions are critically influenced by the type and number of feeder cells used.

The influence of plaque on reaction mechanism of MFP and NaF in vivo

A modified Intra-oral Cariogenicity Test was used to study the influence of plaque on the reaction mechanism of sodium monofluorophosphate (MFP) or sodium fluoride (NaF) in either sound or demineralized enamel in vivo. Volunteer students, wearing mouth appliances holding enamel blocks, rinsed their mouths with MFP or NaF solution (1,000 ppm F-) three times a day. The amount of loosely-bound and acquired fluoride was determined after an experimental period of five days in plaque-covered, demineralized (PCD); clean, demineralized (CD); plaque-covered, sound (PCS); and clean sound enamel (CS). While no measurable loosely-bound fluoride could be found after MFP treatment, NaF caused deposition of a significant amount of alkali-soluble fluoride in all experimental groups. After MFP rinses, fluoride concentration in the enamel was increased in the following order: CS, PCS, CD, and PCD. After NaF treatment, demineralized enamel exhibited a higher fluoride acquisition when compared with sound enamel. Plaque had a minor effect on F- acquisition. It is concluded that demineralization of enamel enhances F- uptake from both NaF and MFP solutions. In the presence of plaque, F- acquisition was additionally increased only after MFP rinses in vivo.

[Indications for corrective operations for maintaining function in post-traumatic deformities of the distal lower leg and foot]

Reconstruction surgery in posttraumatic deformities in the lower leg and the foot is indicated under different aspects: restoration of function, improvement of prognosis, improvement of function and melioration of physical appearance. Technically effective surgical means are available to date, such as: metaphyseal closing and opening wedge osteotomies, diaphyseal step-cut osteotomies, diaphyseal and metaphyseal displacement osteotomies, lengthening osteotomy, external fixation, revision of infections, joint revisions, scar revisions, nerve revisions, plastic skin operations.