SPLENIC ADHERENT CELLS, STIMULATED IN-VITRO, INDUCE THE REACTIVE FORMATION OF LYMPHOID FOLLICLES AND GERMINAL-CENTERS IN DRAINING LYMPH-NODES AFTER SUBCUTANEOUS TRANSFUSION INTO SYNGENEIC MICE

The reactive formation of lymphoid follicles and germinal centres in l ymph nodes, induced by subcutaneous transfer of in vitro activated spl enic adherent cells into syngeneic mice, were studied. Adherent cells were obtained by incubating spleen cell suspensions for 24 h and activ ated by incubating for 1 h in the medium containing keyhole limpet hae mocyanin (KLH) absorbed onto alumina. Some of the treated adherent cel ls were irradiated with 10 Gy x-rays, while others were either not sti mulated or were stimulated with alumina-KLH but killed by repeated fre ezing and thawing. Examination of adherent cell smears immunostained w ith antibodies against, F4/80, Mac-1, Mac-2 and NLDC-145 indicated tha t many adherent cells displayed macrophage markers but few displayed t he interdigitating cell marker. Animals transfused with KLH-treated ad herent cells with or without irradiation showed a marked increase in t he number of lymphoid follicles and germinal centres in draining lymph nodes, whereas those transfused with adherent cells which had not bee n KLH-treated or which had been killed after KLH treatment displayed n o significant change in the number of follicles. These results were in terpreted as indicating that following transfusion, antigen-activated adherent macrophages migrated into the draining lymph nodes and induce d the reactive formation of lymphoid follicles and germinal centres ou tside preexisting follicles.