Clonal priming of human lymphocytes: Specificity and cross-reactivity of cellular immune reactions

Clonal priming in response to chemical and microbial antigens which defines the specificity of cellular immune reactions, was demonstrated by culture techniques. Human leucocyte cultures stimulated with specific antigens typically show peak levels of D.N.A. synthesis after 5 to 7 days in culture. Such primary leucocyte cultures were incubated for 10-20 days, then the cells were gently centrifuged and resuspended in fresh RPMI 1640 with 20% plasma. These secondary or primed cultures typically showed less than 1000 c.p.m. after 48 hours. However, if the original antigenic stimulant was added, specific accelerated responses were seen by 48 hours in the secondary cultures. Lymphocyte clones in these sceondary cultures primed with dinitrophenylated (D.N.P.) antigens (from subjects sensitised to dinitrochlorobenzene) showed enhanced D.N.A. sythesis in response to the same dinitrophenylated antigens and showed varible accelerated responses to related chemically modified antigens. However, D.N.P.-activated clones in these secondary cultures did not show enhanced responses to microbial antigens even though the lymphocytes had been highly responsive to tetanus toxoid and other microbial antigens in primary cultures. The specificity of this clonal activation was further demonstrated by the enhanced response of secondary cultures of tetanus-toxoid-activated clones to tetanus toxoid but not to dinitrophenylated antigens. The abiltty to detect specificity and cross-reactivity of cellular immune reaction has broad implications for investigations of cellular immunity as well as many potential applications in the diagnosis and understanding the patogenesis of inflammatory and neoplastic diseases in which cellular immune discrimination may be involved.