Thymus dependency of bone marrow stem cell proliferation in response to certain antigens

The activity of mouse bone marrow CFU's following systemic injection of antigen has been investigated. In normal mice quiescent CFU's may be triggered into cycle after antigenic challenge. Prior adult thymectomy prevents stimulation of CFU if thymus-dependent antigens are injected but not when thymus-independent antigens or non-specific stimuli are used. Similar results were obtained in congenitally athymic mice. This seems to indicate an independent pathway for CFU triggering for each cell lineage and for T and B cells.