Limiting Dilution Analysis to Helper T-cell Function.

Limiting dilution analysis has been applied to the study of T-cell 'helper' function in vitro. Using the microculture system one can estimate the numbers of (a) 'helper' T cells involved in specific collaboration with B cells and (b) those T cells which are able, on being activated by their specific antigen, to facilitate the response of B cells to another antigen. Such studies have enabled us to demonstrate that: (1) a single helper' T cell was able to activate a single B-cell precursor to detectable antibody production; (2) the `helper' function of primed T cells was radio-resistant; (3) a minimal estimate of `helper' frequencies could be obtained in defined cell populations; (4) non- specific facilitation was directed towards virtually all available B cells of a given specificity if these were challenged with their appropriate particulate antigen; (5) the microculture system offers the opportunity to determine whether specific and non-specific T-cell helper' effects are a consequence of the activity of one T-cell type or of different subpopulations of T cells. [ABSTRACT FROM AUTHOR]