Antigen modulation of the immune response. V. Generation of large memory cells in antigen draining lymph nodes.

We have studied the distribution of memory B cell subpopulations by using 1g velocity sedimentation and adoptive transfer. When the non-antigen-draining mesenteric lymph nodes were examined 4 weeks after intraperitoneal immunization with DNPBGG, large memory cells were present in only very low numbers. However, when the draining parathymic nodes were removed, a significant enrichment of large memory cell activity was seen. When these results were corrected for the cell yields in each 1g separated fraction we found that 59% of the total memory cells were small, 36% medium and 5% large in the mesenteric lymph node preparations and 40% were small, 46% medium and 14% large in the parathymic lymph node suspensions. When popliteal lymph nodes were removed after footpad immunization, 32% of the total memory cell activity was in the small cell fraction while 49% was in the medium fraction and 18% in the large cell fraction. Control experiments were also run to show that the shift in the velocity sedimentation profile of the various memory cell populations was not an artifact of the adoptive transfer system nor a result of selective antigen triggering.From these results it would appear that the size distribution of memory cells depends upon the source of cells studied, large memory cells being found predominantly only in lymph nodes draining the site of antigen injection. Since the large memory cells can also be found in the thoracic duct lymph after footpad immunization but not after intraperitoneal immunization, it is suggested that the larger cells can circulate to other lymphoid tissues but cannot recirculate.