The reactive formation of lymphoid follicles and germinal centres
in lymph nodes, induced by subcutaneous
transfer of in vitro activated splenic adherent cells into syngeneic mice,
were studied. Adherent cells were
obtained by incubating spleen cell suspensions for 24 h and activated
by incubating for 1 h in the medium
containing keyhole limpet haemocyanin (KLH) absorbed onto alumina.
Some of the treated adherent cells
were irradiated with 10 Gy x-rays, while others were either not
stimulated or were stimulated with alumina-KLH but killed by repeated
freezing and thawing. Examination of adherent cell smears immunostained
with
antibodies against, F4/80, Mac-1, Mac-2 and NLDC-145 indicated
that many adherent cells displayed
macrophage markers but few displayed the interdigitating cell marker.
Animals transfused with KLH-treated
adherent cells with or without irradiation showed a marked increase
in the number of lymphoid follicles and
germinal centres in draining lymph nodes, whereas those transfused with
adherent cells which had not been
KLH-treated or which had been killed after KLH treatment displayed
no significant change in the number
of follicles. These results were interpreted as indicating that
following transfusion, antigen-activated adherent
macrophages migrated into the draining lymph nodes and induced the
reactive formation of lymphoid
follicles and germinal centres outside preexisting follicles.