Proliferative response of human CD4+ T lymphocytes stimulated by the lectin jacalin

Area of Science:

• Immunology
• Molecular Biology

Background:

• Jacalin, a Gal beta(1-3)GalNAc-binding lectin, activates CD4+ T cells and inhibits HIV-1 infection.
• Jacalin's interaction with CD4 and its role in T cell proliferation require further elucidation.

Purpose of the Study:

• To investigate the molecular mechanisms and signaling pathways underlying jacalin-induced T cell proliferation and cytokine production.
• To compare jacalin's effects on primary human peripheral blood mononuclear cells (PBMCs) and Jurkat T cell lines.

Main Methods:

• Human PBMCs and Jurkat T cells were stimulated with jacalin.
• Monoclonal antibodies were used to block specific cell surface molecules (CD2, LFA-3, LFA-1, ICAM-1, CD4, CD5).
• Cytokine production (IL-2, IL-6, IFN-gamma) was measured using ELISAs.
• T cell receptor/CD3 complex involvement was assessed using CD3- Jurkat cell variants.

Main Results:

• Jacalin-induced proliferation of PBMCs required cognate T cell-monocyte interaction, with IL-1 and IL-6 unable to substitute for monocyte co-stimulation.
• Blocking studies suggested the involvement of CD2/LFA-3 and LFA-1/ICAM-1 pathways, and anti-CD4 antibodies partially inhibited responsiveness.
• Jacalin induced IFN-gamma and IL-6 in PBMCs, but not IL-2. In contrast, Jurkat cells secreted IL-2, dependent on the T cell receptor/CD3 complex and CD4 expression.

Conclusions:

• Jacalin induces T cell proliferation and cytokine production through complex molecular interactions involving CD4, CD2/LFA-3, and LFA-1/ICAM-1 pathways.
• Distinct signaling pathways are activated in primary PBMCs and Jurkat T cells, highlighting the importance of cellular context in jacalin-mediated responses.
• Jacalin's interaction with CD4 and CD5 molecules is crucial for its biological effects, and these interactions can be inhibited by specific sugars.