Differential requirement for CD2 in IFN-γ production by antigen-stimulated CD4⁻CD8⁺ T cells. A total of 1 × 10⁵ CD4⁻CD8⁺ lymph node cells from H-2^b H-Y mice were stimulated with 1 × 10⁶ B6 male spleen cells in a volume of 0.2 mL with or without IL-2 (20 U/mL). The supernatants from these cultures were collected after 40 hours. The amount of IFN-γ present in the supernatants from H-Y cells with or without the CD2 null mutation are shown. The same experiment was performed for CD4⁻CD8⁺ thymocytes or lymph node cells from H-2^b 2C mice except that these cells were stimulated with 1 × 10⁶ (C57BL/6xDBA/2)F₁ spleen cells. The amount of IFN-γ produced by lymph node cells from H-Y and 2C mice was less than 10 U/mL when these cells were stimulated with female B6 spleen cells (data not shown).