Direct demonstration of CD4 T cell cooperation in the primary in vivo generation of CD4 effector T cells.
ABSTRACT Many observations bear upon the cellular and molecular requirements for CD4 T cell activation. The interaction of CD4 T cells with dendritic cells (DC), central to the induction of most immune responses, is the most studied. However, leukocytes other than DC can dramatically affect the induction and differentiation of CD4 T cells into effector cells. We recently provided indirect evidence that in vivo CD4 T cooperation facilitates the activation of CD4 T cells. Here, we demonstrate that the activation of CD4 T cells, specific for the hen egg lysozyme (HEL)(105) (-120) peptide, is optimally achieved when BALB/c mice are immunized with additional MHC class II-binding HEL peptides in incomplete Freund's adjuvant. This cooperation cannot be mimicked by the coadministration of LPS or of an agonistic antibody to CD40, at the time of immunization. In contrast, OX40-OX40L interactions are necessary for CD4 T cell cooperation in that an OX40 agonistic antibody can replace, and an OX40L-blocking antibody can abrogate, CD4 T cell cooperation in situations where such cooperation would otherwise enhance the activation of CD4 T cells.
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ABSTRACT: We show that the in vivo generation of cytokine-producing CD4 T cells specific for a given major histocompatibility class-II (MHCII)-binding peptide of hen egg lysozyme (HEL) is facilitated when mice are immunized with splenic antigen presenting cells (APC) pulsed with this HEL peptide and another peptide that binds a different MHCII molecule. This enhanced generation of peptide-specific effector CD4 T cells requires that the same splenic APC be pulsed with both peptides. Pulsed B cells, but not pulsed dendritic cells (DCs), can mediate CD4 T cell cooperation, which can be blocked by disrupting OX40-OX40L (CD134-CD252) interactions. In addition, the generation of HEL peptide-specific CD4 T cell memory is greater when mice are primed with B cells pulsed with the two peptides than with B cells pulsed with the HEL- peptide alone. Based on our findings, we suggest CD4 T cell cooperation is important for vaccine design, underlies the phenomenon of "epitope-spreading" seen in autoimmunity, and that the efficacy of B cell-depletion in the treatment of human cell-mediated autoimmune disease is due to the abrogation of the interactions between autoimmune CD4 T cells that facilitates their activation.PLoS ONE 10/2013; 8(10):e77346. · 3.53 Impact Factor
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ABSTRACT: Any physiological system that has as its output an activity that is biodestructive and ridding must have a way of distinguishing the host (self) from that which is other (nonself). The setting in which autoimmunity can be analyzed depends, in part and unavoidably, on the way in which the normal self (S)-nonself (NS) discrimination is accomplished. Any discussion of autoimmunity should include one's view of this latter. To this end, a pathway for the normal S-NS discrimination will be proposed. Then, a mechanism for the determination of effector class will be considered as autoimmune disease is consequent to it. Experiments challenging both the proposed model of normal behavior, as well as that of the extrapolation to autoimmunity, will be cited along with a discussion of some of the elements which, if rendered defective, would result in autoimmunity. The goal is to see how far this particular abstraction based largely on the logic of evolutionary biology can meaningfully guide understanding of the disease.Journal of Theoretical Biology 05/2014; · 2.30 Impact Factor