Production and characterization of cloned T-cell hybridomas that are responsive to Rickettsia conorii antigens.

T-cell hybridomas produced by the fusion of Rickettsia conorii immune T cells to the AKR thymoma BW 5147 produced interleukin-2 when stimulated with the antigens of three different R. conorii strains. One cloned hybridoma responded only to R. conorii antigens, whereas a second and third cloned hybridoma also responded to the antigens of Rickettsia rickettsii Sheila Smith and Rickettsia sibirica 246, respectively. Antigen responses required antigen-presenting cells, and this interaction was major histocompatibility complex restricted. Fluorescence-activated cell-sorter analysis demonstrated that all three hybridomas were of the Thy-1.2+, Lyt-2- phenotype and that two of the three were L3T4+. These data demonstrated the presence of an antigenic epitope that is R. conorii species specific and other epitopes that are common to various members of the spotted fever group which can stimulate interleukin-2 production by T-cell hybridomas.