Bacterial lipopolysaccharides activate immune suppressor cells in newborn mice

Neonatal injection of C57B1/6 mice with bacterial LPS results in an impairment of the ability of splenic lymphocytes to respond to erythrocyte antigens in vitro 4 weeks later. This impairment is due either to a de novo activation of suppressor cells or to an enhancement of the longevity of “naturally occurring” suppressor cells found in the newborn spleen since cells from LPS-injected mice also inhibited normal control responses. The suppressor cells from LPS-injected mice are not macrophages and, by conventional criteria, appear to be T lymphocytes. Results of this study raise questions concerning the effects of suppressor cells on LPS-potentiated antibody formation and the multiplicity of pathways for activation of antibody-forming precursor cells.