Rapamycin decreases lymphoproliferation. (A-D) Serial ultrasounds were performed every 2 weeks to document lymph node volume in cubic millimeters and splenic area in square millimeters, comparing rapamycin-treated with untreated mice. Treated mice showed a statistically significant (P = .05) decrease in lymph node volume after 2 weeks of treatment when compared with control mice (E). Treated mice also showed a statistically significant (P = .03) decrease in splenic area by 4 weeks of treatment when compared with control mice (F). No statistical difference existed between groups at initiation of treatment. Bars represent mean lymph node volume or splenic areas from mice at each time point and error bars represent SEM. Average normal mouse spleen size in unaffected animals was 10 to 20 mm². (A) Representative example of a lymph node prior to treatment with rapamycin. (B) The same node from panel A after 4 weeks of treatment. Initial volume of the node was 114 mm³ and the volume after treatment was 19 mm³, representing an 80% reduction in size. (C) In contrast to panels A-B, a lymph node of a mouse prior to treatment with vehicle. (D) The same node from panel C after 4 weeks. Initial volume of this node was 230 mm³ and the volume after exposure to vehicle was 1242 mm³, representing a 600% increase in size.