Proliferative responses of T cells to TCR and IL-2 are inhibited by the lipid raft component GM1.

(A-B) Plasma membrane compartmentalization into lipid rafts in the presence or absence of GPI-anchored proteins. Lysates of GPI⁺ (A) or GPI⁻ (B) 2.10 T cells were subjected to discontinuous sucrose density gradient ultracentrifugation. Fractions (Fr) were collected from the top of the gradient, and the distribution of CD45, Fyn, Thy-1, and GM1 was analyzed by immunoblotting. Fractions corresponding to lipid rafts and soluble membranes are indicated. (C-D) Immobilized CT inhibits anti-TCR and IL-2–induced proliferation. GPI⁺ and GPI⁻2.10 T cells were cultured in wells precoated with CT (▪), anti–Thy-1 (■), or an isotype control (░) mAb and coimmobilized anti-TcR-Cβ (C) or in the presence of 15 U/mL IL-2 (D).³H-thymidine uptake was assessed after 20 hours of culture.