four different sources were used to produce the factors : a ) cells of a t cell hybrid ( t2d4 ) constitutively secreting igg-bf upon incubation in serum-free medium , b ) t2d4 cells incubated with mouse monoclonal igg1 antibody in order to induce in vitro the production of isotype-specific igg1-bf , c ) t2d4 cells induced in vivo by passage as ascites in nude mice and incubated in serum-free medium , and d ) in vivo alloantigen-activated t cells ( atc ) incubated in serum-free medium .
C1327616
secreting
C0007634
cells