title: Limiting dilution analysis of helper T-cell function.
abstract: 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) nonspecific 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 differenct subpopulations of T cells.
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D000921:Antibody-Producing Cells / Q000528:radiation effects; D001402:B-Lymphocytes / Q000276:immunology; D002352:Carrier Proteins; D002452:Cell Count; D004912:Erythrocytes / Q000276:immunology; D006241:Haptens; D006433:Hemocyanins / Q000276:immunology; D007156:Immunologic Memory; D051379:Mice; D008808:Mice, Inbred CBA; D008819:Mice, Nude; D010527:Perissodactyla / Q000276:immunology; D012756:Sheep / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D002352:Carrier Proteins; D006241:Haptens; D006433:Hemocyanins