Suppression induction in vivo by a T helper clone?

Reporting the Implementation of the Three Rs in European Primate and Mouse Research Papers: Are We Making Progress?

It is now more than 20 years since both Council of Europe Convention ETS123 and EU Directive 86/609?EEC were introduced, to promote the implementation of the Three Rs in animal experimentation and to provide guidance on animal housing and care. It might therefore be expected that reports of the implementation of the Three Rs in animal research papers would have increased during this period. In order to test this hypothesis, a literature survey of animal-based research was conducted. A randomly-selected sample from 16 high-profile medical journals, of original research papers arising from European institutions that featured experiments which involved either mice or primates, were identified for the years 1986 and 2006 (Total sample = 250 papers). Each paper was scored out of 10 for the incidence of reporting on the implementation of Three Rs-related factors corresponding to Replacement (justification of non-use of non-animal methods), Reduction (statistical analysis of the number of animals needed) and Refinement (housing aspects, i.e. increased cage size, social housing, enrichment of cage environment and food; and procedural aspects, i.e. the use of anaesthesia, analgesia, humane endpoints, and training for procedures with positive reinforcement). There was no significant increase in overall reporting score over time, for either mouse or primate research. By 2006, mouse research papers scored an average of 0 out of a possible 10, and primate research papers scored an average of 1.5. This review provides systematic evidence that animal research is still not properly reported, and supports the call within the scientific community for action to be taken by journals to update their policies.

Immunodominance in the CTL Response Against Minor Histocompatibility Antigens: Interference Between Responding T Cells, Rather than with Presentation of Epitopes

We have investigated mechanisms involved in immunodominance of the CTL response of C57BL/6 (B6) mice against cells of BALB.B origin. This transplantation barrier consists of at least 40 minor histocompatibility (H) Ags. Insufficient presentation of nondominant epitopes in the presence of dominant epitopes was investigated as a possible mechanism for immunodominance. Ag presentation was assessed by recognition of dendritic cells of BALB.B origin, MLC restimulatory capacity, and quantification of cell surface presentation by peptide elution from intact cells. Cells from BALB.B mice, which fail to elicit CTL against nondominant epitopes, presented nondominant epitopes to a similar extent as cells from minor H congenic mice; the latter do elicit CTL against nondominant minor H Ags. Nevertheless, presentation of nondominant and dominant epitopes by the same APC appeared to be an important factor for immunodominance to occur, since simultaneous immunization with the epitopes on separate cells elicited CTL against both types of epitopes. This suggested that immunodominance is determined in the interaction between different responding T cells and the APC. Support for this was obtained in an in vitro model in which the CTL response against a nondominant epitope was inhibited by the concomitant response against a dominant epitope. This study suggests that immunodominance in the CTL response against certain minor H Ags results from interference between T cell responses and not from insufficient presentation of peptide epitopes. The study also provides an in vitro model for further investigations of the immunodominance phenomenon.

Frequencies and interactions of regulatory T cells. I. The balance between help and suppression regulates the primary immune response to keyhole limpet hemocyanin in vitro

Frequencies and efficiencies of regulatory T cells from non-immunized mice were estimated in several assay systems differing from each other in cellular composition and antigen dose (NIP-KLH). The NIP-specific and total IgM responses were quantified. Using 10(4) syngeneic B cells and 50 micrograms/ml NIP-KLH, helper (Th) cells from 5 day immune donors were detected in frequencies of 1:3000-1:4000 in lymphnode and spleen T cells, with an efficiency of 70-90 ng IgM/Th cell in C57B1/6 mice. In non-immune spleen T cells, Th cells were observed in frequencies of 1:16,000-1:38,000, with comparable efficiency, but these Th cells appeared suppressed at increased T cell doses. Polyclonal activation led to the appearance of multiple independently regulated populations of Th cells with similar efficiencies. In the presence of 10(5) syngeneic spleen cells, treated once with anti-Thy-1 antibody and complement and 50 micrograms/ml NIP-KLH, suppressor activity was observed in the same T cell population. Similar to help, suppression fluctuated with increasing T cell numbers. Using 1 x 10(6) spleen cells and 50 micrograms/ml NIP-KLH as assay system, T cells enhanced the responses. Again, several independently regulated populations were observed, with efficiencies slightly higher than those of the above-described Th cells. By maintaining the cellular components of the assay system constant (10(4) B cells) and titrating the antigen, Th cell frequencies showed little variation up to 100 micrograms/ml NIP-KLH and were always suppressed at higher T cell numbers. At 200 micrograms/ml NIP-KLH, the frequency was increased to approximately 1:2000, and not suppressed, i.e., was identical to the frequency observed in mice immunized 5 days previously. Efficiencies increased with increasing doses of antigen. The results strongly indicate that regulatory T cell function shows "plasticity", in the sense that the appearance and the frequencies of helping and suppressing T cell populations highly depend on the micro-environment present in culture.

Two distinct subsets of patients with systemic lupus erythematosus

This study was undertaken to examine the levels and function of peripheral blood immunoregulatory T cell subpopulations in systemic lupus erythematosus (SLE). T cell subpopulations can be distinguished by the T cell differentiation antigens CD4 (recognized by the monoclonal antibodies OKT4 or Leu3) and CD8 (recognized by the monoclonal antibodies OKT8 or Leu2). All SLE patients tested had normal percentages of CD8 cells in their peripheral blood. The SLE patients, however, fell into two groups based on their CD4 cell numbers. Fifty-five percent of the SLE patients had normal levels of CD4 cells (Group A) and therefore normal CD4/CD8 cell ratios, whereas 45% of the SLE patient population had markedly depressed CD4 cell levels (Group B) and significantly low CD4/CD8 cell ratios. T cells from normal donors and SLE patients were further examined for their ability to stimulate allogeneic normal B/M phi cells to secrete IgM in the presence of pokeweed mitogen (PWM). Utilizing this assay system two forms of immunosuppression were observed: (1) that mediated by high concentrations of purified CD4 cells and (2) that mediated by CD8 cells. High concentrations of purified CD4 cells, added to a constant number of allogeneic normal B/M phi cells, suppressed PWM-stimulated IgM synthesis. Group B SLE patients, with significantly low CD4 cell numbers, had defective CD4 cell-mediated suppression which was concentration dependent. This result was confirmed in a study using identical twins discordant for SLE. In this case CD4 cells from the SLE twin did not induce immunosuppression at a high concentration of CD4 cells whereas similar concentrations of CD4 cells from the normal twin resulted in suppression. SLE patients (Group A) with normal levels of CD4 cells had normally immunosuppressive CD4 cells. Suppression mediated by CD8 cells was demonstrated by the fact that removal of CD8 cells resulted in enhanced IgM synthesis induced by the remaining CD4 cells. Although all the SLE patients in this study had normal peripheral blood levels of CD8 cells, SLE Group A patients had defective CD8 cell suppression whereas CD8 function appeared to be normal in Group B patients. These results suggest that in SLE patients with depressed CD4 cell numbers (Group B) there is a corresponding defect in CD4 cell function. We demonstrate that in SLE Group B patients, defective suppression is due to a subset of T cells that bear the CD4 antigen. The SLE patient population (Group A) with normal CD4/CD8 ratios and normally functioning CD4 cells, however, appear to have normal CD4 cell-mediated suppression but defective CD8 suppressor cell function.

MHC-restricted minimal regulatory circuit initiated by a class II-autoreactive T cell clone

The in vivo administration of a self-class II-reactive Th clone MS202 derived from C3H into syngeneic mice resulted in the suppression of both primary and early secondary antibody responses against T cell-dependent antigens. The suppression was due to the generation of antigen-nonspecific Ts cells in the recipient, as the splenic T cells from the mice treated with MS202 were able to strongly suppress the in vitro secondary antibody response of primed syngeneic spleen cells. The dose-response curve of suppression indicated the generation of an effector type Ts that directly suppressed Th. The surface phenotype of Ts was Ly-1+,2-, L3T4+, I-J-. The presence of Ly-1+,2+ T cells was not required to induce the suppression. The suppression was strictly restricted to H-2k, as F1 Ts cells were able to suppress the response of C3H but not of B6 B cells helped by the same F1 Th cells. The experiments with chimeric mice indicated that the direct target of Ts is an MHC-restricted Th but not a B cell or APC. The results indicate the existence of a minimal regulatory circuit where an MHC-restricted Th induces a preprogrammed Ts that in turn directly suppresses Th with the same MHC-restriction specificity. The induction of and suppression by Ts appeared to be due to the direct recognition of MHC restriction sites of Th cells.