Lipopolysaccharide suppresses immune complex retention by follicular dendritic cells without cytological alterations

Follicular dendritic cells (FDC) are peculiar cells only located inside lymph follicles and which may be characterized by complex dendritic evaginations retaining high quantities of immune complexes by Fc and C3b receptors. After lipopolysaccharide (LPS) injection in mice the retention of gold-labelled immune complexes was abolished in draining lymph nodes. In order to examine the possibility that the transport of immune complexes to lymph follicles was impaired, we isolated FDC from lymph nodes and incubated them in presence of gold-labelled complexes: no or strongly reduced retention was then observed at the ultrastructural level. This LPS-induced impairment of immune complex fixation by FDC is not due to morphological alteration to the cells but to the inhibition of their Fc and C3b receptors. Further, LPS induces changes in the composition of the lymphocyte population in lymph follicles as higher numbers of blast cells and plasmocytes are observed after treatment.