title: Frequency of allogeneic helper T cells responding to whole H-2 differences and to an H-2K difference alone.
abstract: Limiting dilution analysis was used to determine the frequency of splenic T cells that are stimulated by alloantigen to give help in a primary antibody response to SRBC. Several haplotype combinations were tested. A semilogarithmic plot of the fraction of nonresponding culture as a function of the number of T cells added to excess B cells gave a straight line intercepting with the origin. Thus a single cell-type was limiting, which was required to help B cells respond to SRBC. The frequency of syngeneic precursors of T helper cells specific for SRBC ranged from 1/10,000 to 1/55,000 with a mean of about 1/20,000. Allohelpers generated by whole H-2 differences gave precursor frequencies that ranged from 1/1000 to 1/7000 with a mean of about 1/2500. Thus allohelpers to whole H-2 differences were approximately 8-fold more frequent than SRBC-specific helpers. When the stimulation was limited to the H-2K difference between the mutant B6.C-H-2ba and wild-type B6, frequencies of from 1/2600 to 1/7900 allohelpers were found with a mean of about 1/5000, approximately half the frequency of allohelpers to whole H-2 differences. Thus some, but probably not all, of the magnitude of allogeneic halp can be attributed to the high frequency of helper T cells that respond to a given alloantigen.
mesh_terms: D000818:Animals; D000917:Antibody Formation; D001402:B-Lymphocytes / Q000276:immunology; D006183:H-2 Antigens / Q000276:immunology*; D007519:Isoantigens / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008819:Mice, Nude; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D006183:H-2 Antigens; D007519:Isoantigens