Beta 2-integrin dependent aggregate formation between LB T cell lymphoma and spleen cells: assessment of correlation with spleen invasiveness.

LB is an aggressive T cell lymphoma which rapidly invades the spleen and lymph nodes of BALB/c mice after s.c. inoculation. We previously reported that mAb directed against the beta 2 chain of the leukocyte function-associated antigen-1 (LFA-1) adhesion molecule (CD18) blocked the invasion of LB cells into the spleen but not into the lymph nodes. The same antibody also blocked in vitro aggregate formation between normal spleen cells and LB cells. However, aggregate formation between normal lymph node cells and LB cells was not detected, regardless of ratio. In an attempt to evaluate the association between aggregate formation and tumor invasion of the lymphoid organs, we have now extended the study. Intravenous injection of anti-CD18 mAb, which blocked spleen invasion by LB cells, also blocked the formation of ex vivo aggregates, spontaneously generated in spleen, but not in lymph node, cell suspensions of BALB/c mice s.c. inoculated with LB cells. In contrast, mAbs unable to block spleen invasion were ineffective inhibitors of both in vitro and ex vivo aggregate formation between spleen and LB cells. Spleens of nude mice that did not provide a supportive environment for lymphoma invasion, were also deficient in target cells forming aggregates with LB cells. In line with this observation, enriched T cells formed more aggregates with LB cells than did enriched non-T cells, indicating the lymphoma's preferential binding to splenic T cells.(ABSTRACT TRUNCATED AT 250 WORDS)