The stimulation of low-affinity, nontolerized clones by heteroclitic antigen analogues causes the breaking of tolerance established to an immunodominant T cell epitope.

H-2K mice injected, intravenously in saline or intraperitoneally in incomplete Freund's adjuvant, with large quantities of the immunodominant I-E(k)-restricted epitope from moth cytochrome c (MCC) 88-103 fail to respond to subsequent immunization with this epitope when administered in complete Freund's adjuvant. This state of tolerance can be broken by immunization with certain MCC 88-103 analogues that are heteroclitic antigens as assessed on representative MCC 88-103 specific T cell clones. In this paper, the mechanism of breaking tolerance by heteroclitic antigens was investigated. The following observations were made: (a) T cell hybridomas derived from tolerance-broken animals required higher concentrations of MCC 88-103 to be stimulated than hybridomas derived from normal immune animals, suggesting that they have T cell receptors (TCRs) of lower affinity; (b) in contrast to normal immune animals whose MCC-specific TCRs are typically Vbeta3(+)/Valpha11(+), none of the hybridomas derived from tolerance-broken animals expressed Vbeta3, although they were all Valpha11(+). Also, the Vbeta complementarity determining region 3 (CDR3) regions from the tolerance-broken animals did not contain the canonical structure and length characteristics of the normal MCC 88-103 immune repertoire; and (c) adoptive transfer and tolerization of MCC-specific Vbeta3(+)/Valpha11(+) transgenic T cells followed by immunization with heteroclitic antigen failed to terminate the state of tolerance. Collectively, these data strongly suggest that the mechanism involved in breaking tolerance in this system is the stimulation of nontolerized, low-affinity clones, rather than reversal of anergy. Further support for this mechanism was the finding that after activation, T cells apparently have a lowered threshold with respect to the affinity of interaction with antigen required for stimulation.

Cd4(+) T cell response to Leishmania spp. in non-infected individuals.

T cell mediated immunity is known to play a central role in the host response to control intra-cellular pathogens. This work demonstrates the presence of specific CD4(+) T cells to Leishmania spp. antigens in peripheral mononuclear cells of naïve individuals (normal volunteers from non-endemic regions). The responder population was expanded by generation of antigen-specific T cell lines, which were produced by repeated stimulation with fixed promastigotes and autologous irradiated PBMC as antigen presenting cells. The leishmania-T cell lines were shown to proliferate in response to different species of the parasite (L. amazonensis, L. braziliensis, and L. donovani), but not to other recall antigens such as Candida albicans or tetanus toxoid. A preferential expansion of IFNgamma and IL-2 producing Th1-like T cells was observed. The leishmania-reactive cells were distributed between CD4(+) CD45RA(+) ("naïve") and CD4(+) CD45R0(+) ("memory") populations. Although limiting dilution analysis showed a precursor frequency 3 times lower within the naïve compartment, similar numbers of T cell lines were derived from both purified subpopulations. This study using leishmania-specific CD4(+) T cell lines produced from normal individuals should provide information on cellular immune responses that are triggered by the parasite and how infection impacts the naïve T cell repertoire.

A single intramuscular injection with an adenovirus-expressing IL-12 protects BALB/c mice against Leishmania major infection, while treatment with an IL-4-expressing vector increases disease susceptibility in B10.D2 mice.

Experimental infection of the susceptible BALB/c (H-2d) mouse with the intracellular parasite Leishmania major induces a predominant Th2-type T cell response that eventually leads to death. In contrast, the resistant B10.D2 (H-2d) strain develops Th1 cells that control parasite replication and disease. In this study, we tested the ability of a recombinant adenovirus vector-expressing IL-12 to skew the immune response in a Th1 direction and prevent leishmaniasis in susceptible mice. We report that BALB/c mice treated with the Ad5IL-12 vector on the same day as parasitic challenge are significantly protected against leishmaniasis and acquired long-lasting immunity, because upon rechallenge with L. major parasites they were resistant to disease. The vector-derived IL-12 expression was transient and highly localized to the tissue after i.m. injection; it caused an increase in the number of Ag-specific IFN-gamma-secreting lymphocytes and enhanced NK cell activity in the draining popliteal node. In contrast, resistant B10.D2 mice given i.m. injections with a recombinant adenovirus-expressing IL-4 displayed greater susceptibility to disease, and severe lesions were produced in some of the infected animals. These results suggest the potential use of recombinant adenoviruses expressing cytokines as potent immunomodulatory agents for the generation of protective immune responses against intracellular pathogens.

Radicais livres e manitol sublingual / Free radicals and sublingual mannitol

Foi estudada a açäo do manitol por via sublingual em um grupo de pacientes, em cujo sangue foram determinados radicais livres, lipoperóxidos e ceruloplasmina. Observou-se que: 60 minutos após a administraçäo de 1.800 mg do manitol houve uma reduçäo estatisticamente significativa dos radicais livres, que se normalizou 120 minutos depois. A açäo lipoperoxidativa significativa dos radicais livres, que se normalizou 120 minutos depois. A açäo lipoperoxidativa foi mais lenta, sendo observado um decréscimo significante duas horas após a ingestäo. Näo houve alteraçäo na atividade da ceruloplasmina. Tais achados sugerem a possibilidade de emprego do manitol por via sublingual

Radicais livres após teste ergométrico / Free radicals after the ergometric test

Foi realizado um estudo ergométrico em 14 pacientes fisicamente condicionados. Os radicais livres foram dosados antes por quimioluminescência no sangue, imediatamente após o teste e 15 minutos após o teste. A seguir, três dias após, o teste foi repetido de maneira similar com os pacientes ingerindo manitol por via sublingual. Observou-se uma elevaçåo significativa dos radicais livres nas amostras após exercício, retornando ao normal aos 15 minutos pós-teste. O manitol diminuiu significativamente a elevaçåo dos radicais livres pós-exercício. A ceruloplasmina se elevou após a ingeståo de manitol, o que pôde explicar a queda dos radicais livres

Sesquióxido de germânio e agregaçäo plaquetária / Germanium sesquioxide and platelet aggregation

O sesquióxido de germânio, substância imunomoduladora e varredora de radicais livres, foi testado em 23 indivíduos normais por via sublingual, em doses de 75 mg. A inibição da agregação plaquetária foi evidente demonstrando a possibilidade futura de ser testada esta substância como antiagregante plaquetária.