Monoclonal IgG antibodies influence the migration patterns of lymphocytes in vivo

Monoclonal antibodies (MoAb) are useful therapeutic agents for the treatmen t of a variety of human disorders, although the effector mechanisms respons ible for the outcome of an efficient immunotherapy remain unclear. This stu dy was designed to address the early effects of MoAb on the migration patte rns of lymphocytes in vivo. The clearance profiles and tissue distribution of In-111-labelled rat lymph node cells were examined in both normal and de complemented allogeneic and semi-allogeneic recipients pre-injected with Ig G2b (R3/13) or IgG2a (R2/15S) MoAb directed against the RT1A(a), the classi cal class I major histocompatibility complex antigen of the DA rat. Both Mo Ab were equally effective in not only augmenting the removal of DA and (DA x PVG)F-1 cells from the circulation and promoting their subsequent localiz ation within the liver but also causing a significant degree of cell lysis during the early phase of cell clearance, even in decomplemented recipients . Although R3/13 and R2/15S are known to target erythrocytes differently in normal and cobra venom factor (CVF)-treated animals, no differences were o bserved in the migration behaviour of lymph node cells in allogeneic or sem i-allogeneic hosts pre-injected with the same MoAb. Since rat lymphocytes e xpress a much higher level of the RT1A(a) antigen as compared with erythroc ytes; we could not exclude a possible role of residual complement component s in the circulation of CVF-treated rats that may have accounted for the ob served antibody-dependent effects on target lymphocytes. On the basis of th ese findings we believe that the design and methodology employed in our pre sent experimental opsonization system were inadequate to define clearly the mechanisms responsible for antibody-mediated removal and destruction of ta rget lymphocytes in vivo.