Lyt‐Phenotype Conversion of Cytotoxic T Lymphocytes Specific for the A and E Class II Major Histocompatibility Complex Molecules

The Lyt‐l + (high) Lyt‐2^± (low) primary cytotoxic T lymphocytes (CTL) specific for A(A_αA_β) molecules and the Lyt‐l ⁺Lyt‐2⁺ primary E(E_αE_β)‐specific CTL are both shown to become Lyt‐l⁻ Lyt‐2 ⁺ effector cells after secondary in vitro stimulation. Thus CTL specific for class II major histocompatibility complex molecules exhibit the same Lyt‐phenotype shift as class‐I‐specific CTL do. The data suggest that either both class‐I‐specific and class‐II‐specific CTL follow the same differentiation pathway or regulatory cellular interactions allow only Lyt‐l ⁻Lyt‐2⁺ cells to differentiate to secondary CTL.