Recognition of Rat Dendritic Cells by a Monoclonal Antibody

A mouse monoclonal IgM antibody reactive with dendritic cells (DC) from the Brown Norway (BN) rat was prepared. This antibody (1F119) binds to a membrane-bound antigen present on DC from thoracic duct lymph, spleen, thymus, and lymph node. The antigen is present only in low density on 5% of splenic macrophages (M phi) and absent from peritoneal M luminal diameter. In situ, the antibody exhibits a strong reactivity towards DC in the thymic medulla, whereas no reaction is observed with cortical cells. Furthermore, cells positive for 1F119 can be identified in T-cell areas of spleen, lymph node, and Peyers' patches. 1F119 was genetically restricted in that a strong reactivity was found with DC from rats of the RT1n and RT1u haplotypes, an intermediate reactivity with the RT1c haplotype, only a weak reactivity with the RT1l and RT1b haplotypes, and no reactivity with the RT1a and RT1k haplotypes. The relatively weak reactivity of 1F119 with respect to the RT1l haplotype also appeared from a weak binding of 1F119 to DC from Lewis rats, as was assessed by FACS analysis. This result was comparable to the binding of OX3 (RT1.Bl and RT1.Bu) to DC from BN rats. Studies performed on thymus sections of recombinant rat strains indicate that 1F119, despite its apparent specificity for DC, reacts with a polymorphic RT1.B product.     

Susceptibility to clinically manifest cyclosporine A (CsA)-induced autoimmune disease is associated with interferon-gamma (IFN-γ)-producing CD45RC+RT6− T helper cells

Lethally irradiated Lewis (LEW) rats reconstituted with syngeneic bone marrow and given CsA for a 4-week period, develop, upon withdrawal of CsA, a graft-versus-host-like disease, so-called CsA-induced autoimmunity (CsA-AI). This T cell-mediated autoimmune disease is thymus-dependent; it is generally held that this disease is a consequence of aberrant T cell recovery brought about by CsA. In this study we determined mononuclear cell subsets phenotypically by tri-colour flow cytometry. A strong decrease in recent thymic emigrants (Thy1.1⁺, TCR αβ⁺) was observed as a consequence of CsA treatment, eventually resulting in decreased absolute peripheral T cell numbers. In these rats no altered CD4:CD8 T cell ratio was observed before onset of CsA-AI; CD4⁺ and CD8⁺ cells consisted predominantly of monocytes (CD4^dim+, TCR αβ⁻) and natural killer cells (CD8⁺, TCR αβ⁻), respectively. LEW rats, x-irradiated, syngeneic bone marrow-reconstituted and treated with CsA, showed a marked and persistent, relative expansion of mature CD45RC⁺, RT6⁻ Th cells. In contrast, Brown-Norway rats treated in a similar fashion, or LEW rats subjected to either CsA treatment or x-irradiation, did not show a comparable expansion of mature CD45RC⁺, RT6⁻ Th cells, nor did these animals develop CsA-AI. The CD45RC⁺, RT6⁻ Th cells produced IL-2, and moreover constituted the only Th subset producing IFN-γ upon stimulation, and therefore were considered as Th1-like effector cells. These results are consistent with the view that a persistent preponderance of Th1 cells and not the mere presence of autoreactive cells determines whether or not clinically manifest CsA-AI will occur.     

Impaired immune responsiveness in Plasmodium berghei immune mice

Mice immunized against Plasmodium berghei parasites by drug-controlled infection exhibited decreased immunoresponsiveness against rabbit red blood cells (RRBC). Increasing RRBC antigen dose increased responsiveness, but agglutinating anti-RRBC antibodies of the IgG class remained undetectable. Clearance of colloidal carbon from the bloodstream of malaria-immunized mice was not different from controls. Removal of all the persistent parasites from immune mice did not restore responsiveness until 140 days after treatment, suggesting that the parasite per se did not influence responsiveness directly. Because of this, and because of the fact that priming of mice with RRBC before P. berghei immunization was not more effective than priming after immunization, it was concluded that antigen uptake and subsequent presentation were not impaired in P. berghei immune mice, in contrast to infected mice. Anti-RRBC antibodies were detected in serum of P. berghei immune mice, but regulation of responsiveness to RRBC by transfer of such immune mouse serum was not found. Immunoglobulin levels, especially of the IgG2 and IgG3 subclass were elevated in sera of P. berghei immune mice, which indicated an LPS-like polyclonal activation. The results also suggest that during drug-controlled infection, which leads to immunity against infection, a state of B-cell tolerance is induced.     

Defective de novo thymocyte maturation in cyclosporin A (CsA)-induced autoimmunity: expression of costimulatory and activation molecules

Lethally x-irradiated Lewis rats, reconstituted with syngeneic bone marrow and transiently treated with CsA for 4 weeks, will develop an autoimmune disease about 2–3 weeks after cessation of CsA therapy. CsA-induced autoimmunity is a thymus-dependent and T cell-mediated autoimmune disease. CsA is thought to generate autoreactive T cells by interference with negative selection in the thymus; x-irradiation is required to eliminate the peripheral autoregulatory T cell circuit. In this study we re-evaluate the effect of CsA on thymic atrophy and thymocyte maturation. Subsequently we examine the expression of costimulatory and activation molecules (CD2, CD5, CD11a, CD11b, CD25, CD28, CD43, CD54, OX-40, RT-1A, RT-1B and RT-1D) during distinct maturational stages in order to detect possible clues to the observed effects of CsA on thymocyte maturation and selection. The results revealed that CsA blocks maturation of double-positive TCR^int to double-positive TCR^high thymocytes and preferentially inhibits the development of mature CD4 single-positive thymocytes. Furthermore, CsA administration resulted in a reduced expression of the costimulatory CD2 molecule. Although it is a matter of debate whether this defective CD2 expression is involved in the aberrant maturation and selection of thymocytes, it is speculated that reduced costimulation via CD2 may influence differentiation into distinct T cell subsets.     

Protective and pathological activity in serum of mice developing resistance to Plasmodium berghei infection

Summary The serum from mice developing resistance against Plasmodium berghei infection using chemotherapeutic treatment has been analysed in vivo and in vitro. During the immunization period pathological as well as protective activities which could be transferred by serum were generated. The pathological activity, which was defined as destruction of erythrocytes in normal recipient mice, was generated early in the immunization procedure, peaked at day 21, and decreased to undetectable levels by day 35. After reinfection of the donor mice the pathological activity reappeared in the serum, and was maintained for at least 56 days. Analysis of the transferred serum samples showed the presence of anti-erythrocyte antibodies (ELISA), but no correlation with the in-vivo anti-erythrocyte effect could be found. The anti-erythrocyte effect of the serum samples indirectly increased the parasitaemia in the recipient mice through the induction of reticulocytosis. The protective effect of the serum samples could only be detected in samples taken from animals beyond day 61 of the immunization procedure. This net protective effect was reflected in a decreased parasitaemia at 7 days after challenge of the recipient mice with P. berghei infected erythrocytes. The protective activity of the serum was correlated with high titres of anti-erythrocyte antibodies. Anti-erythrocyte antibody titres were strongly correlated with titres against heterologous red blood cells as well as total immunoglobulin content of the serum samples, indicative of polyclonal activation of lymphocytes. Except for IgGl, all (sub-) classes were elevated during the immunization procedure, of which IgG3 was abundant. After immunity was obtained these immunoglobulin levels remained high, and the relative amount of IgGl in the serum was restored.     

Anti-inflammatory,Analgesic and Ulcerogenic Properties of S-(+)-Ibuproxam,Racemic Ibuproxam-β-cyclodextrin and S-(+)-Ibuproxam-β-cyclodextrin

The anti-inflammatory, analgesic and gastric mucosal damage-inducing activities of S-(+)-ibuproxam, and S-(+)-ibuproxam-β-cyclodextrin, new propionic acid derivatives, and racemic ibuproxam-β-cyclodextrin were investigated in three animal models and compared with those of racemic ibuproxam, racemic ibuprofen and its optical enantiomer S-(+)-ibuprofen. The anti-inflammatory activities of racemic ibuprofen, S-(+)-ibuprofen and racemic ibuproxam in carrageenan-induced paw oedema in rats were almost equipotent and slightly greater than those of S-(+)-ibuproxam and S-(+)-ibuproxam-β-cyclodextrin, and significantly greater than that of racemic ibuproxam-β-cyclodextrin. In abdominal constriction tests in mice, the analgesic effects of racemic ibuproxam, S-(+)-ibuproxam, racemic ibuproxam-β-cyclodextrin and S-(+)-ibuproxam-β-cyclodextrin were significantly less pronounced than those of racemic ibuprofen and S-(+)-ibuprofen. Ulcerogenic activity of S-(+)-ibuproxam-β-cyclodextrin in rats was found to be significantly weaker than that of racemic ibuproxam-β-cyclodextrin, racemic ibuproxam and S-(+)-ibuproxam and, most notably, weaker than those of racemic ibuprofen ans S-(+)ibuprofen. These results indicate that S-(+)-ibuproxam-β-cyclodextrin could be a novel potent anti-inflammatory and analgesic agent with a therapeutic index more favourable than that of the classical non-steroid anti-inflammatory drugs ibuprofen and ibuproxam.     

Infection with rat cytomegalovirus (CMV) in the immunocompromised host is associated with the appearance of a T cell population with reduced CD8 and T cell receptor (TCR) expression

Infection with human cytomegalovirus (HCMV) mostly results in a chronic subclinical infection; the immune system is unable to eliminate the virus and is apparently in equilibrium with the persistent virus. In the immunosuppressed host this equilibrium is disturbed, resulting in clinical infection. Rat cytomegalovirus (RCMV) infection in its host can be used as a model for HCMV infection. Using flow cytometry we examined the effect of acute RCMV infection on the composition of leucocyte subsets in the peripheral blood of both immunocompetent and immunosuppressed (5 Gy total body irradiation) Lewis rats. Special attention was paid to the natural killer (NK) cells and the CD8⁺ T cells known to be involved in the control of viral infections. Furthermore, we determined the presence of leucocyte subsets in the internal organs by immunohistochemistry. In immunocompetent rats, infection caused a small increase in NK cells and a large increase in CD8⁺ T cells. In contrast, infection of immunosuppressed rats caused a marked increase in NK cells and a small increase in CD8⁺ T cells, consisting of T cells with reduced expression of both CD8 and TCR. This phenomenon is characteristic of anergic CD8⁺ T cells, possibly explaining the ability of the virus to escape elimination by the immune system. The increase of NK cells in the peripheral blood of immunosuppressed, RCMV-infected rats could also be detected in kidney, liver, lung and pancreas, but not in salivary gland. This could explain the long persistence of infectious virus in the salivary gland.