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Trypanosoma cruzi kinetoplastid membrane protein-11 (KMP-11) is able to induce protective immunity in mice. In humans, T-cell immunity during Chagas disease has been documented using parasite antigens allowing the identification of specific CD8+ T cells. However, little is known about the CD4+ T-cell response during the evolution of the disease. In this paper, the induction of a natural CD4+ T-cell response against the KMP-11 protein in T. cruzi infected humans was studied to assess whether this parasite-derived protein could be processed, presented and detected as a major histocompatibility complex class II restricted epitope. The results show that helper T cells from 5 out of 13 chagasic patients specifically produced interferon-γ after exposure to the KMP-11 antigen, whereas healthy donors and non-chagasic cardiopathic patients did not respond. This is the first description of T. cruzi KMP-11 protein recognition by CD4+ T cells in chronic chagasic patients.Immunology and Cell Biology (2009) 87, 149–153; doi:10.1038/icb.2008.76; published online 28 October 2008 [ABSTRACT FROM AUTHOR]

In the early phases of an immune response, T cells of appropriate antigen specificity become activated by antigen-presenting cells in secondary lymphoid organs. Two-photon microscopy imaging experiments have shown that this stimulation occurs in distinct stages during which T cells exhibit different motilities and interactions with dendritic cells (DCs). In this paper, we utilize the Cellular Potts Model, a model formalism that takes cell shapes and cellular interactions explicitly into account, to simulate the dynamics of, and interactions between, T cells and DCs in the lymph node paracortex. Our three-dimensional simulations suggest that the initial decrease in T-cell motility after antigen appearance is due to ‘stop signals’ transmitted by activated DCs to T cells. The long-lived interactions that occur at a later stage can only be explained by the presence of both stop signals and a high adhesion between specific T cells and antigen-bearing DCs. Furthermore, our results indicate that long-lasting contacts with T cells are promoted when DCs retract dendrites that detect a specific contact at lower velocities than other dendrites. Finally, by performing long simulations (after prior fitting to short time scale data) we are able to provide an estimate of the average contact duration between T cells and DCs.Immunology and Cell Biology (2007) 85, 306–314. doi:10.1038/sj.icb.7100054; published online 10 April 2007 [ABSTRACT FROM AUTHOR]

Summary Cytotoxic T cells normally express major histocompatibility complex class I molecules, to which their T cell antigen receptors are restricted. Therefore, a single cytotoxic T cell can not only act as a cytolytic effector cell, but also as an antigen-presenting cell for other cytotoxic T cells of the same or a different clone. In the present paper, we used a murine cytotoxic T cell clone, 10BK.1, recognizing the ovalbumin-derived peptide OVA257-264 in combination with H-2Kb to investigate the consequences of reciprocal antigen presentation by these cytotoxic T cells. These cells proliferate after incubation with the relevant peptide in the absence of added accessory cells, indicating reciprocal antigenic peptide presentation by the cytotoxic T cell. We found that reciprocal lysis of these cells was dependent on the time point of incubation with antigen. We did not observe reciprocal lysis of cytotoxic T cells used 30 days after the last restimulation with antigen. In contrast, 10BK.1 cells used two days after the last restimulation showed an increased capacity for reciprocal lysis. The lytic capacity decreased with time after restimulation. Reciprocal lysis of 10BK.1 cells depended on reciprocal peptide presentation by at least two 10BK.1 cells. Recognition of the antigenic peptide, together with class I molecules on the surface of classical syngeneic target cells did not induce lysis of freshly stimulated 10BK.1 cells, suggesting that reciprocal lysis was not just a consequence of re-activation of the cytotoxic T cells. Reciprocal destruction of freshly activated 10BK.1 cells proceeded independent of CD95/CD95 ligand. Despite an increased secretion of tumour necrosis factor-α by 10BK.1 cells on day 2 after antigen stimulation, compared with cells on day 30 after stimulation, tumour necrosis factor-α was not responsible for the reciprocal destruction of freshly stimulated 10BK.1 cells. Lysis of preactivated 10BK.1 cells was... [ABSTRACT FROM AUTHOR]