Fig. 4

CD86 expression after in vitro stimulation of naive B cells by L1-Env nanoparticles. Naive Env-specific PGT121 (left panel) or wild-type (wt, right panel) B cells (2 × 10⁵) were incubated for 18 h with L1-Env and lentiviral VLPs at various dilutions normalized to their Env concentration (1.6–1000 ng/ml). Lentiviral VLPs were used as a positive control for BCR-dependent stimulation of Env-specific B cells, and 2 µg/ml LPS served as a positive control for polyclonal stimulation of B cells. Negative controls included unstimulated (mock) cells or cells incubated with a mixture of L1-VLPs and soluble Env at concentrations ranging from 1.6 to 1000 ng/ml of each protein. After 18 h, cells were stained for viability, and B cell activation was assessed by measuring the upregulation of CD86 on CD19 + cells via flow cytometry.