Expansion of γδ-T cell induced by anti-CD2 mAb S5.2 requires the presence of IL-12 and occurs as a consequence of an increase in γδ–T-cell absolute numbers.

Mitogen-stimulated PBMC cultures were initiated as described above. All cultures were primed with IFN-γ on the day of culture initiation (day 0) in the presence of anti-CD2 mAb S5.2 (or IgG_2a isotype control, not shown). In addition, IL-12, PBS control, or antihuman IL-12 mAb (or isotype control for anti–IL-12 mAb, not shown) was included in these cultures. Twenty-four hours later (day 1), all cultures were stimulated with mitogenic OKT3 and IL-2. After 7 days, both the percentage and the absolute number of γδ-T cells were determined in cultures. Viable T cells were first identified by gating on the CD3-PE⁺ and PI⁻ populations. (A) Percentage of T cells staining with an anti-γδ-TCR–FITC mAb is shown in each histogram. (B) Absolute number of γδ-T cells found in indicated culture conditions (mean ± SD) determined in quadruplicate. These results are representative of experiments performed using materials obtained from at least 8 different persons. (C) Mitogen-stimulated PBMC cultures were initiated as described above (day 0, IFN-γ; day 1, OKT3 and IL-2). On day 0, either IL-12 (10 U/mL) or PBS (−) was added to cultures. Likewise, anti-CD2 mAb S5.2 (or IgG_2a isotype control, not shown) was added at the indicated concentration (μg/mL). After 14 days, absolute numbers of both αβ-T cells and γδ-T cells in cultures were determined by multiplying the total cell number in culture by the percentage of αβ- and γδ-T cells, as measured by FACS. Data are presented as fold expansion (mean ± SD) over starting numbers of αβ-T cells (open bars) and γδ-T cells (solid bars), determined in triplicate. Results are representative of experiments performed using materials obtained from at least 8 different persons.