title: Histocompatibility antigen-activated cytotoxic T lymphocytes. II. Estimates of the frequency and specificity of precursors.
abstract: Using limiting dilutions of responding cells in mouse mixed leukocyte cultures, we obtained direct estimates of the minimum frequency of precursors of cytotoxic T lymphocytes (CTL.P) for a variety of antigens. Depending on the strain combination, there were as many as 4-15 CTL.P reactive to DBA/2 among 10(4) lymph node cells. Taking into account that only 5-10% of peripheral T lymphocytes have the potential to develop into cytotoxic T lymphocytes (CTLs) (6), this implies that at least 1-2% of all CTL.P are responsive to any given H-2 haplotype difference. Precursors of cytotoxic cells thus have the same high frequency of cells reactive to alloantigens of the major histocompatibility complex as found among proliferating cells in graft-vs.-host reactions and mixed lymphocyte interactions. The frequencies of CTL.P reactive to xenoantigens (rat) or trinitrophenyl-modified self were less than half the frequency of alloreactive CTL.P. A minority of the CTL.P specific for one H-2 haplotype were also reactive to a third party H-2 haplotype, presumably on the basis of recognition of shared determinants. By dilution of sensitized cells from single microcultures, it was shown that a single CTL.P undergoes a minimum of three to four cell divisions and generates at least 8-16 CTLs after antigenic activation.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000276:immunology; D002478:Cells, Cultured; D002999:Clone Cells; D005260:Female; D006412:Hematopoietic Stem Cells; D006649:Histocompatibility Antigens / Q000276:immunology*; D007958:Leukocyte Count; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology / Q000276:immunology*
chemical_list: D006649:Histocompatibility Antigens