Stimulation of B-lymphocytes by endotoxin. Reactions of thymus-deprived mice and karyotypic analysis of dividing cells in mice bearing T 6 T 6 thymus grafts.

Thymus-independent B lymphocytes were shown to play the main role in the transformation response of mouse spleen cultures to endotoxin (LPS). Spleen cells from mice thymectomized at 6 to 8 weeks, lethally irradiated, and reconstituted with syngeneic bone marrow (TxXBM) reacted normally to LPS, while the responses to phytohemagglutinin and ConA were markedly depressed. The reaction to LPS, however, was temporarily depressed in the TxXBM mice and was fully recovered only 4 weeks after treatment. This latent period may be necessary for processing of the reacting cells. Karyotypic analysis of spleen cultures from mouse chimeras with T6T6 thymus grafts showed that only 1.2% of the LPS-stimulated cells were of thymus origin, as compared to 29.7% reacting to PHA and 12.2% to sheep red blood cells.