ICAMs Are Not Obligatory for Functional Immune Synapses between Naive CD4 T Cells and Lymph Node DCs

Area of Science:

• Immunology
• Cell Biology
• T cell immunology

Background:

• Immune synapses between T cells and antigen-presenting cells (APCs) are vital for adaptive immunity.
• ICAM-1 and ICAM-2 are known LFA-1 ligands involved in cell adhesion and immune responses.
• Their specific roles in T cell priming in vivo remain incompletely understood.

Purpose of the Study:

• To investigate the in vivo function of dendritic cell (DC) ICAM-1 and ICAM-2 in naive CD4 T cell priming and differentiation.
• To determine if LFA-1-mediated adhesion to DC ICAMs is required for T cell activation and effector differentiation.

Main Methods:

• Utilized transgenic mouse models.
• Employed intravital imaging techniques.
• Examined CD4 T cell priming and differentiation in skin-draining lymph nodes following DC stimulation.

Main Results:

• Surprisingly, deficiency of ICAM-1 and ICAM-2 on CD40-stimulated lymph node DCs did not hinder their ability to arrest and prime naive CD4 T cells.
• T cell activation, proliferation, and early differentiation into Th1 and Tfh effectors occurred normally.
• Functional T cell receptor (TCR)-specific T cell synapses were formed without LFA-1-mediated adhesiveness to DC ICAMs.

Conclusions:

• LFA-1-mediated T cell adhesiveness to dendritic cell ICAMs is not essential for the formation of functional helper T cell synapses.
• Naive CD4 T cell priming, proliferation, and early differentiation into effector T cells in vivo do not require DC ICAMs.