Chapter 6 - Limiting Dilution Assays for the Separation, Characterization, and Quantitation of Biologically Active Particles and Their Clonal Progeny

Abstract

This chapter discusses the limiting dilution assays (LDA) for the separation, characterization, and quantitation of biologically active particles and their clonal progeny. LDAs detect binary responses generated by BAPs in individual in vivo or in vitro cultures within groups of replicate cultures that vary in the dose of the test preparation from which the BAPs are sampled. Relative frequency LDAs, however, also incorporate an accompanying physicochemical assay for particles of a general type defined by their structural morphology or other physicochemical characteristics and called physicochemically observable particles (POPs). In absolute number LDAs, the number of POPs is never known because any physicochemical assay that could conceivably be used to observe them is not performed because of impracticality or impossibility. As a result of the unstable nature of most biological preparations, it is impractical to assay repeatedly the same biological sample. It is possible to assay repeatedly the same biological population by performing, either simultaneously or serially, a sequence of LDAs on a sequence of biological samples with one assay for each sample.