Frequency of influenza-responsive cytolytic T-lymphocyte precursors in the thymus and spleen of unprimed mice.

Limiting dilution culture conditions were established which allowed the differentiation and quantitation of influenza-specific cytotoxic T-cell precursors (CTL.Ps) from naive mouse spleen and thymus. One in 49,000 nucleated spleen cells and 1 in 40,000 thymocytes responded to stimulation with influenza-infected, anti-Thy 1.2 and complement-treated spleen cells, in the presence of ConA-stimulated cell supernatant, with the production of cytotoxic effector cells. These frequencies are 4- to 15-fold higher than those for influenza-responsive B cells in the relevant lymphoid compartments, and it is argued that major quantitative discrepancies may exist in the sizes of the B- and CTL-receptor repertoires.