Tohoku J. Exp. Med., 2011, 223(3)

Formation and Aggregation of Lipid Rafts in γδ T Cells Following Stimulation with Mycobacterium tuberculosis Antigens

HE-ZUO LÜ,^1,2 AN-YOU ZHU,² YONG CHEN,² JIE TANG² and BAI-QING LI²

¹Central Laboratory, the First Affiliated Hospital of Bengbu Medical College, Anhui, P.R. China
²Department of Immunology, Bengbu Medical College, and Anhui Key Laboratory of Infection and Immunity at Bengbu Medical College, Anhui, P.R. China

Lipid rafts are plasma membrane microdomains that are implicated in diverse signaling pathways in immune cells. Based on the distinct types of T-cell receptors, two T-cell subpopulations have been identified: αβ and γδ T cells. In humans, γδ T cells represent a relatively rare T lymphocyte population but play a critical role in the immune response to infection by Mycobacterium tuberculosis. It has been demonstrated that Mycobacterium tuberculosis antigens (Mtb-Ag) preferentially activate γδ T cells. Thus, we investigated whether lipid rafts are involved in the Mtb-Ag-mediated activation of γδ T cells. Human peripheral blood mononuclear cells (PBMCs) were stimulated with Mtb-Ag, and expression of a lipid raft marker ganglioside GM1 (GM1) was determined by flow cytometry. The aggregation of lipid rafts was evaluated by laser confocal microscopy. Non-stimulated fresh PBMCs minimally expressed GM1 (6.55 ± 2.01%) and had no aggregated rafts in γδ T cells. Mtb-Ag stimulation gradually increased the expression of GM1 in a time-dependent manner. At 72 h, the majority of γδ T cells expressed GM1 (88.69 ± 7.55%). Furthermore, accompanied with the increased expression of GM1, aggregation of lipid rafts became gradually visible in γδ T cells. The aggregated rafts, however, were not evenly distributed and only occurred over a small portion of GM1-positive cells. Pretreatment with methyl-β-cyclodextrin, a cholesterol-depleting reagent, completely inhibited the Mtb-Ag-mediated aggregation of lipid rafts. These results demonstrate that lipid raft aggregation occurs in Mtb-Ag-activated γδ T cells, suggesting that lipid rafts are involved in activation of γδ T cells.

keywords —— Mycobacterium tuberculosis antigens; γδ T cells; lipid rafts; methyl-β-cyclodextrin; ganglioside GM1; flow cytometry

© 2011 Tohoku University Medical Press

===============================

Tohoku J. Exp. Med., 2011, 223, 193-198

Correspondence: Bai-Qing Li, Depatment of Immunology and Ahui Key Laboratory of Infection and Immunity, Bengbu Medical College, 2600 Dong Hai Avenue, Bengbu, Anhui 233030, P.R. China.

e-mail: baiqingli@bbmc.edu.cn