Kinetic assay of cytotoxic T lymphocyte clones. I. Methodology and data analysis.

A kinetic assay for cytotoxic T lymphocyte (CTL) clones expanded briefly in culture is described. The Hill equation for allosteric kinetics is used to fit curves to dose-response data. In this assay, K0--the target cell concentration required for half-maximal velocity of killing--is determined for clones generated from a population's most frequent CTL precursors. Because each clone's K0 is a constant under given conditions and a description of relative cytolytic efficiency, K0 values can be used to compare the clonal composition of disparate or dynamic populations. The parameter n is the target concentration exponent in the Hill equation and the slope of the line in the Hill plot. This parameter further specifies the shape of a clone's dose response curve, describing a clone's responsiveness to changes in target cell concentration. Because the assay is designed for small, undetermined effector cell concentrations, maximum velocities are not compared. The method described herein requires minimal supplies, equipment, and biological materials.