Culture of mouse spleen cells with mATG and IL-2 shows initial depletion at 1 day followed by a proliferative response after 4 days. Normal C57BL/6 mouse splenocytes were cultured alone, with 100 μg/mL mATG, or with rabbit IgG in the presence or absence of 200 U/mL IL-2, and total viable cells were enumerated at various times following initiation of culture as described in “Methods.” (A) Viable cell numbers obtained 1, 2, 4, 5, and 6 days following culture initiation of splenocytes with or without mATG in the presence or absence of exogenous IL-2. (B) Viable cell numbers obtained 1, 2, 3, 4, 5, and 7 days following culture initiation of splenocytes with either mATG or rabbit IgG, both in the presence of exogenous IL-2. Data shown are representative of at least 6 separate experiments.