Anti-CD2 mAb S5.2 induces γδ–T-cell expansion through an agonistic and not a blocking interaction with CD2.

(A) Anti-CD2 mAb S5.2 does not induce γδ–T-cell expansion by disrupting a CD2–CD58 interaction. Mitogen-stimulated PBMC cultures were initiated as described above, now with the inclusion of IL-12 (day 0, IFN-γ, IL-12; day 1, OKT3 and IL-2). On day 0, either PBS (−), mAb S5.2 (mouse IgG_2a), antihuman-CD58 mAb L066.4 (mouse IgG_2a), or mouse IgG_2a isotype control was added separately to identical cultures. After 14 days, cultures were analyzed using FACS. Viable T cells were first identified by gating on the CD3-PE⁺ and PI⁻ populations. Percentage of T cells staining with an anti-γδ-TCR–FITC mAb is shown in each histogram. Results are representative of experiments performed using materials obtained from at least 3 different persons. (B) Immobilized, but not soluble, anti-CD2 mAb S5.2 can induce γδ–T-cell expansion in mitogen-stimulated, monocyte-depleted PBMC cultures. Monocyte-depleted PBMC cultures were initiated as described above, stimulated on day 0 with IFN-γ, IL-12, and either soluble or plastic-immobilized mAb S5.2. Twenty-four hours later (day 1), cultures were mitogenically stimulated with IL-2 and plastic-immobilized OKT3. After 21 days, cultures were analyzed using FACS; the percentage CD3-APC⁺/γδ-TCR-FITC⁺ cells in each dot plot was indicated. Immobilized or soluble IgG_2a (isotype control for mAb S5.2) had a minimal effect on γδ–T-cell expansion (not shown). Results are representative of experiments performed using materials obtained from at least 3 different persons.