Mechanisms of dendritic cell-induced T cell proliferation in the primary MLR assay
I L Tourkova1, Z R Yurkovetsky, M R Shurin
1Department of Pathology, Clinical Immunopathology-CLSI, University of Pittsburgh Medical Center 5725 CHP MT, 200 Lothrop Street, 15213, Pittsburgh, PA 15213, USA.
Insights
Dendritic cells (DCs) activate T cells through membrane structures, not protein synthesis. This research clarifies key mechanisms in T cell activation for immune response studies.
Area of Science:
- Immunology
- Cell Biology
Background:
- Dendritic cells (DCs) are crucial antigen-presenting cells.
- Their function is often assessed by T cell proliferation in mixed leukocyte reaction (MLR) assays.
Purpose of the Study:
- To investigate the mechanisms underlying DC-induced T cell activation in primary MLR assays.
- To identify factors critical for DC stimulatory capacity.
Main Methods:
- Examined agents interfering with DNA synthesis, membrane organization, and protein synthesis.
- Utilized paraformaldehyde fixation and cycloheximide pretreatment of DCs.
- Assessed Staphylococcus aureus-mediated DC activation, including in IL-12 knockout mice.
Main Results:
- Live DCs are essential for T cell proliferation; irradiation does not affect stimulatory capacity.
- Paraformaldehyde fixation abolishes DC-induced T cell proliferation, highlighting membrane organization's importance.
- Protein synthesis inhibition (cycloheximide) does not impair DC T cell activation.
- Staphylococcus aureus activation enhances T cell proliferation independently of IL-12 production.
Conclusions:
- DC membrane structures are critical for antigen presentation and co-stimulation.
- Physical organization of DC plasma membranes plays a vital role in T cell recognition and activation.
Abstract:
DC are unique antigen presenting cells, and their ability to induce proliferation of T cells in a mixed leukocyte reaction (MLR) assay is commonly used for the evaluation of their function. To determine the mechanisms involved in DC-induced T cell activation in a primary MLR assay, a variety of different agents were examined in this study that interfere with DNA synthesis, membrane organization, protein synthesis, and maturation induced by bacterial products. While only live DC were able to induce T cell proliferation in the MLR assay, irradiation of DC did not influence their stimulatory capacity. Fixation of DC membrane with paraformaldehyde resulted in a loss of DC capacity to induce T cell proliferation demonstrating that physical organization of the plasma membranes plays an important role in the induction of T cell activation. In addition, the pretreatment of DC with cycloheximide revealed that protein synthesis was not critical for the ability of DC to activate T cells. Finally, Staphylococcus aureus-mediated activation of DC significantly increased T cell proliferation and this effect was not dependent on IL-12 production of DC since DC generated from IL-12 knockout mice were not different from wild type DC. In summary, these data suggest that DC membrane structures are responsible for the antigen presentation and co-stimulation and play a key role in T cell recognition and activation by DC.
