Induction of NKR-P1A expression on cultured CD34⁺ CD33^lo thymocytes. Cultures of CD34⁺ CD33^lo thymocyes were set up as described in Fig 6. The correlated expression of NKR-P1A and CD13 was analyzed by flow cytometry on electronically gated CD44^bright large cells at the indicated time points. Percentages of NKR-P1A⁺ CD13⁺ cells recovered at days 3, 4, 5, and 7 were 27%, 22%, 7%, and 5%, respectively, in cultures lacking IL-2; and 29%, 40%, 30%, and 40%, respectively, in cultures containing IL-2. The correlated expression of NKR-P1A and CD56 was analyzed on electronically gated CD44^bright large cells recovered under both culture conditions at day 7. Background fluorescence was determined by sequential staining with isotype-matched (IgG₁) irrelevant MoAbs, FITC-conjugated goat antimouse IgG₁, and PE-conjugated isotype-matched irrelevant MoAbs.