In vivo localization of antitumor lymphocytes separated with Dolichos biflorus lectin

We examined the in vivo localization of Con A sup-cultured murine splenocytes separated with Dolichos biflorus agglutin (DBA) to elucidate the mechanism underlying the high antitumor efficacy of cells which are not agglutinable with DBA (DBA- cells). First, 51Cr-labeled DBA-separated cells were injected intravenously (i.v.) into mice and then the tissues were collected for gamma counting. DBA- cells showed significant localization in the spleen, compared with DBA+ cells. This was further confirmed by injecting Thy1.2-positive DBA- cells into Thy1.1 congenic mice. Furthermore, after [3H]TdR-labeled DBA-separated cells had been injected i.v., the spleens of the recipients were fixed, sectioned and processed for autoradiography to determine in which region of the spleen the labeled cells had accumulated. We found that DBA- cells were especially concentrated in the white pulp of the spleen, where lymphocytes are localized before being recirculated. These results suggest that DBA- cells exert strong antitumor activity in vivo partly due to their localization in the spleen and partly to the high incidence of active recirculation.